That itself is the question: what makes them into something else, and where is the line drawn?

That is connected to the heap paradox. I don't know where the line is drawn, and I certainly can't lay down a general a priori criterion. There is a sense of when someone is no longer with us. As stated, that says nothing about him ]other than that in my view he is mistaken. He of course should continue to hold his position, because that is what he truly thinks.
From the standpoint of Judaism, I tend to think that the main thing is loyalty to Jewish law, and the surrounding outlook questions are less important. To be sure, even that is not a sharp criterion, since my picture of Jewish law is also different from the Haredi one. But in my opinion there is no serious doubt that their Judaism has value, and therefore there is value in someone returning in repentance to Haredi Judaism even if, in my opinion, he is mistaken about many things. I do not think there is a single person in the world who thinks exactly like me (and maybe that's a good thing). Does that mean everyone is a heretic and their Judaism has no value in my eyes? That is a problematic approach.

Rabbi, why "maybe that's a good thing"?

I was half joking. Half serious, because my outlook on how truth is can lead some people to leave (and others it leads to stronger faith).

Either way. If their outlook is nonsense and because of that they remain, what value does that nonsense have?

How is this connected to the heap paradox? After all, the only value that N has is commandment observance; that is the only N in the story, and N+1 will never occur?

What does it mean that their outlook is nonsense? It has problematic dimensions even in my view, but there are also correct things in it. A Haredi person is religious + Haredi-ness. His religiosity is roughly like mine. As for the additions, there are such details and such details.

There are many parameters in the religious and Haredi outlook. I don't know how much is needed for something to have value and count as Jewish religiosity.

"A Haredi person is religious + Haredi-ness" ???
The Rabbi is basically claiming that Judaism can tolerate endless additional layers with no end or purpose; that is, any content added onto Judaism will always be expressed as a legitimate addition. Why not say "whoever adds, detracts," or, as Elchanan Wasserman defined Religious Zionism, "idolatry in partnership"?

Dear Benjamin. As I wrote, not every addition detracts, only certain additions. Beyond that, even if it detracts, that does not mean the detraction completely nullifies all the value of his faith and religious service. In your opinion, does someone who adds some custom (even a foolish custom) thereby lose all the value of his Judaism?
These things are very simple, and I don't understand the hair-splitting we are doing here.

Regarding what the Rabbi wrote, "maybe that's a good thing," about people who do not share his outlook, because some of them leave because of it: still, why does the Rabbi care that there are people who leave as a result of the Rabbi's outlook? After all, on the other hand the Rabbi maintains that a person should follow his intellect and is compelled to do so. Does the Rabbi prefer that they not be compelled to leave, but instead be compelled to keep the religion?

You remind me of the Vizhnitzer saying: it is better to fail in baseless love than in baseless hatred. I always add that best of all is not to fail at all.
And now I will add for you: if one nevertheless does fail, then indeed it is preferable to fail in baseless love.
Take careful note.

Wonderful answer! I liked it.