I went through what Rabbi Tabbady wrote, and in my humble opinion he is really not right.
His claims about how and in what context to read the responsa quoted by Rabbi Melamed are not only not compelling, but it is entirely possible that Rabbi Melamed learned them precisely within that framework, and that these responsa are speaking about exactly that situation. And his conclusion is completely correct.
If he would only neutralize his principled decision (and I think not from today, despite what he says at the end) against Rabbi Melamed, he would see that there is nothing to his claims.

I’m surprised why the Rabbi writes that conversion without acceptance of the commandments is absolute nonsense.
Even in the Achiezer responsa he instructs to convert in such a situation.
And the Netziv too, in part 5, responsum 46, recognizes such a conversion in Jewish law and in practice (though unlike the Achiezer he does not say to convert ideally in such a situation).
So why is this nonsense in the Rabbi’s view?

It is nonsense because it is clear that there is no such conversion. And in my opinion that is also not what is written in almost all of the sources brought in this context (as far as I know; perhaps only Rabbi David Zvi Hoffmann raises such a possibility). Beyond that, I explained above that sources from halakhic decisors do not really impress me.

Even if there is such a thing as conversion without observance of the commandments, why convert? Better that he remain a non-Jew and his children not be obligated in commandments. Especially since there are views that he is drilling a hole in the boat, bringing disasters, destroying worlds, and delaying redemption.
Not to mention that in conversions for the sake of marriage, it is better that he remain a gentile, and then the Jewish side will violate far lighter prohibitions than if he converts.
And in general, what is the meaning of such a conversion? If he does not believe, what is the point of religious conversion? Conversion should come from faith. How is this different from someone coerced into Christianity because of persecution? Even Christianity understood this, and today they do not baptize just anyone.

Ask whoever performs conversions that way.

I went again through all of section 268 in Yoreh De'ah.
And I did not find at all, neither in the Shulchan Arukh nor in the Rema, that the convert is obligated to keep all the commandments or even some of them.
Only that he accepts upon himself the principle that there is punishment if one violates the commandments and good reward if one keeps them.
And they also elaborate with him on the prohibition of idolatry and belief in one God, etc.
So from where does the Rabbi derive that he is obligated at all to keep the commandments in practice?
Or that he obligates himself to keep them in practice?
He only undertakes to accept the principle of reward and punishment, and of course it is recommended to him to observe and merit reward and not commit transgressions and incur punishment.
Pardon me.
Maybe it is a simple question, but still—where does the Rabbi get that he must observe them? Or at least obligate himself or want to observe them in practice?

That is exactly what is called commitment to the commandments. What does it mean that he accepts upon himself the principle of reward and punishment? Does that depend on him? The Holy One, blessed be He, rewards and punishes. He is declaring that he understands that the commandments obligate him and that there is reward and punishment for them. Acceptance of the commandments is not an undertaking to fulfill them in practice, since even a Jew by birth—and even one who is obligated—does not fulfill everything in practice. This is entry into the world of those who are obligated, and the sanctions are an expression of that. There is no need for actual observance, and that is not a condition in conversion.
Beyond that, the Shulchan Arukh need not mention acceptance of the commandments, because that is the essence of conversion and not a condition in the conversion procedure. The Shulchan Arukh addresses someone who wants to convert and tells him how to do it. But it does not say that he needs to want to convert. He doesn’t want to? Then don’t convert. Likewise, in Choshen Mishpat it is not mentioned that one needs intent to acquire; only the methods of acquisition are brought. Why? Because the intent to acquire is the essence of the acquisition. Someone who does not want to acquire should not acquire. So too, someone who does not want to keep commandments is not converting.
The main source is the Talmud, which says that one who accepts everything except for one matter is not a convert (see Bekhorot 30b).
See a brief overview here: https://www.zomet.org.il/?CategoryID=263&ArticleID=254
But they do not sharpen the point there (and perhaps they erred in this) that the whole discussion is only about the question whether within the conversion process there needs to be an act of accepting the commandments, and whether that is indispensable. On that there is a dispute, as brought there. But that in no way concerns acceptance of the commandments itself, which is the essence of conversion. A convert is someone who comes to accept the commandments upon himself. True, the actual declaration of this at the time of conversion is not an indispensable condition according to some views. A common mistake.

How is it the essence of conversion when there are views that it is entirely rabbinic?
The essence of conversion is joining the Jewish people.
(and according to Rav Saadia Gaon, being willing to endure what the Jewish people go through).

There is no opinion whatsoever that it is rabbinic. Did you read what I wrote?

“Accepts everything except one thing” means that the person converting wants the religious court to make him Jewish except for the prohibition of pork, for example.
That he will not be obligated in that one thing.
That is impossible.
He is obligated in everything and will receive reward for the commandments and punishment for transgressions.
He agrees to enter that framework.
And when he is a gentile, obviously he is not in that framework.
But he is not specifically committing to actual observance; rather, he agrees to enter this binding framework that carries reward and punishment alongside it.

The Chavot Yair writes that acceptance of the commandments is rabbinic.

Even without knowing it, it is clear to me that he did not write that.

Has the Rabbi read Rabbi Re’em’s booklet on the subject of conversion?

No.

Why? Do you not see value in reading the booklet because you do not think the arguments are even worth examining? Or perhaps you already agree with his position (in favor of converting minors, and more), and therefore do not see value in reading it? Or is it simply that you do not have time?
Which option is the correct one?

Most Russians are traditional, including the non-Jews among them, in the sense that they believe in God and that He gave the Torah to Moses. It could be that they think it is preferable to be a Jew in Gehenna than a non-Jew in paradise.

I’m not familiar with that.

How did you determine that most Russians are traditional? Most of them are secular. From atheists and deists to people who do not believe that the Sages had any authority whatsoever. There are also Christians among them, and among them too the majority are not believers.
Actually, when Russians do believe, they become devout Haredim.
Those who believe but keep nothing are mainly Mizrahim.

What is the rule regarding accepting the conversion of a rabbi who converts according to a view different from mine?
Do we have to accept it? But in my opinion it is not a conversion.
Do we not have to accept it? It sounds like it would be very hard to function that way.

You are completely right, and that is why I wrote my article that stirred up an uproar about Rabbi Druckman’s conversions:
https://mikyab.net/%D7%9B%D7%AA%D7%91%D7%99%D7%9D/%D7%9E%D7%90%D7%9E%D7%A8%D7%99%D7%9D/%D7%A9%D7%A2%D7%A8%D7%99-%D7%92%D7%99%D7%95%D7%A8-%D7%A2%D7%9C-%D7%90%D7%9C%D7%99%D7%9E%D7%95%D7%AA-%D7%95%D7%9B%D7%95%D7%95%D7%A0%D7%95%D7%AA-%D7%98%D7%95%D7%91%D7%95%D7%AA
I argued there that they act violently, because they impose on the whole public conversion norms that most halakhic decisors do not agree with, violently seize control of the gates of entry into the Jewish people, and force all of us into the problem you described.
But one has to distinguish between two types of cases: A. A religious court that, in its assessment, thought the convert had accepted the commandments and therefore converted him—in that case, if I disagree with their assessment, I still have to accept their ruling. They are the ones who sat in judgment, and therefore their ruling is what counts. B. A religious court that does not require acceptance of the commandments and converted him—in my opinion that convert is a complete gentile, and one should not relate to the actions of that court at all.
Moreover, in case B I would not dismiss the claim of the well-known dayan from Ashdod who held that a religious court that converts this way is wicked (not because of the view itself—he has the right to think as he does, but because of the violence), and therefore its conversions are invalid for that reason as well. However, in Rabbi Druckman’s system they claimed that they do require acceptance of the commandments, and it is only that in practice the converts usually do not keep most of them; if so, that belongs to the first category and not the second.

I met them and I work with them. The Pew survey also found similar findings.
The Rabbi disqualifies categorically, and I say every case should be judged on its own. (Even in the most lenient religious courts. It does not depend on the religious court but on the convert himself.) I met a female convert who went to marry a gentile in a civil wedding in the Czech Republic, but when I heard her talk about her conversion I am not sure the conversion was invalid. A convert who reverts is still a convert.
I worked with a man who put on tefillin every day but was married to a non-Jewish woman. He knew he was committing a transgression. One day his son came to work. I did not know the son was a gentile, so I wanted to show him something in a Humash. His father said that his son was forbidden to study Torah.
My conclusions are:
A. Each case on its own merits. Even if the convert reverted, that does not mean he does not believe and did not understand that his conversion was acceptance of the commandments.
B. Our problem is with the traditionalists. If the traditional Jews among the Jewish people kept every Sabbath like Yom Kippur, the Russians too would keep every Sabbath like Yom Kippur.

I too, before I met them, had all the stereotypes the Rabbi has about them and thought the conversions were invalid. Today my opinion is much less forceful.

I did not disqualify categorically. Not in the article and nowhere else. On the contrary, I wrote that after the conversion one should not disqualify sweepingly, because every case is judged on its own merits.

Yes, but even when one examines each case on its own merits, the examination cannot be based on the convert’s conduct today, since even if a convert reverted, his conversion is still valid. One can determine that the conversion did not take effect only if the convert does not believe in a commanding God, in which case one can determine that even at the time of the conversion he did not believe, and so it was all an act. If the convert is traditional (that is, he believes in God who was revealed at Sinai and gave us the Torah as preserved in tradition), the doubt remains whether at the time of conversion he accepted all the commandments upon himself or not, and I would not rule out that he in fact did accept them, even if today his behavior is bad.

Correct. So what is the claim?

Since your last responses, Rabbi Melamed has published additional articles that substantiate his position, and not only the bringing of a whole line of later authorities who agree with him.
As for the issue itself, you did not correctly understand Rabbi Melamed’s position. He certainly holds that acceptance of the commandments is essential to conversion; he only holds that the meaning of “acceptance of the commandments” is not a commitment to observe the commandments in practice, but an understanding that these commandments obligate him.
It seems that you yourself wrote this in the comments above: "He is declaring that he understands that the commandments obligate him and that there is reward and punishment for them. Acceptance of the commandments is not an undertaking to fulfill them in practice, since even a Jew by birth—and even one who is obligated—does not fulfill everything in practice. This is entry into the world of those who are obligated, and the sanctions are an expression of that. There is no need for actual observance, and that is not a condition in conversion."
If so, what is your attitude toward his position?

I wrote a column about this, and there I clarified my position. I also raised two possibilities as to what Rabbi Melamed meant, and this was one of them—the one with which I agree.

See column 469.