It’s important to understand the context: Parmenides himself claimed to solve the paradox by erasing it completely through the assumption that there is no plurality or change in the world. In other words, Parmenides thought the paradox is forced on anyone who is not rational and does not correctly recognize the exclusivity of logic as the criterion for interpreting reality. If one recognized the exclusivity of logic, the problem would disappear, in his view.
Aristotle (and on this issue Michi is influenced by him) thought the paradox could be removed without the heavy price tag Parmenides proposed (giving up plurality and change).
Plato, by contrast, proposes an intermediate model according to which the existence of plurality and change in our world does indeed create an unavoidable paradox, but from this one should not conclude that we must give up the assumption of their existence.

I argued here in the past that Aristotle’s explanatory strategy (and that of his successors down to our own day, among them Hegel, Rabbi Kook, and Michi himself) is nothing but the other side of the Parmenidean coin. Parmenides, in other words, bequeathed to his opponents the basic fallacy created by him.

From the statement “what is, is, and what is not, is not,” Steinitz, in the name of Parmenides, derives that there is no creation ex nihilo (because out of non-being, which is not, nothing can come), and derives the law of conservation of matter (because into non-being, which is not, nothing can disappear), along with other strange claims such as “there is matter everywhere” and “everywhere the density of matter is identical and maximal.” I don’t understand this, and I’m not sure there’s anything to understand.

Maybe Steinitz follows Parmenides’ own line of reasoning that there cannot be change in the world, and therefore Bibi cannot be replaced?

Regards, Levingoras

But Steinitz himself was at times a stinking leftist, so according to you how did he change over to the right-wing side? Difficult indeed.

The argument goes like this:
What is, is; and what is not, is not.
“What is” was never created, because if it were created, there are two possibilities: either what is came from what is, or what is came from what is not. But if it came from what is, then it already existed beforehand, and was not created just now. And if from what is not—how could it come into being? After all, we already agreed: what is not—is not.
“What is” will never disappear, because if it disappears into what is, then it still is—and so it has not disappeared. And if it disappears into what is not, how could it disappear? After all, we already agreed that what is not, is not.
“What is” is perfect and fills everything. Because if it does not fill everything, we must claim that in some place there is an absolutely empty void, meaning that there is nothing there at all. This claim is equivalent to saying that “in some place there is no being,” since what is cannot be not. Likewise, we also cannot say that in that place there is non-being, for we already agreed that non-being cannot exist.
It therefore follows that the entire world is full of being, and it cannot be that there are “gaps” in the world, or places that being does not fill.
And by the same reasoning: “being is uniformly dense”—for how could being be less dense in one place than in another? If its density in one place is less than in another, that means that in that place there is less being relative to the same volume. And what would occupy the volume not taken up by being? If there is being there, then it fills everything completely and the density will be equal in all places. If there is non-being there, then there cannot be non-being there, since non-being is not.
Since there is no “non-being” in the world, it follows that the world is full of “being” at maximal density. The resulting picture is that the whole world resembles one huge black hole. It is all full of uniform “being” of infinite density, with no movement or occurrence within it—exactly like a star that has turned into a black hole. And if there is no movement or shifting, that means nothing in the world changes, for how could it change without movement? The world, then, is still and frozen in place; it is in exactly the same state it was a minute ago, a year ago, and even a thousand years ago, and so it will remain forever, since it cannot change—“There is nothing new under the sun,” says Ecclesiastes; nothing new, there never was anything new and never will be anything new, and there is no sun either—so Parmenides declares.

Hello Matan.
Don’t you see where the bug is here?
The basic point is that the claim that something was created from non-being is meaningless nonsense. The intent is that it was not created from anything. When people say “something from nothing,” they do not mean that nothing was the thing from which it was created, but rather that there was no thing from which it was created. It’s like saying that God is “the cause of Himself,” when in fact the intention is that He has no cause. And there has been no shortage of philosophical hairsplitting over the term “cause of Himself,” and it is all nonsense (already Hume in his book An Enquiry Concerning Human Understanding points this out).
Beyond that, there is another mistake here: that empty space is a non-being that does not exist. That’s just wordplay. You can call space being or non-being; it’s a matter of definition.
In short, Greek philosophical hairsplitting, as expected.

Some of the atheists actually do say that the world was created from nothing.

And some of the flies around me also say bzzzzzzz…

The mistake is simple.
The connection between the properties of being and the world we experience has no basis whatsoever.
The properties of being that Parmenides describes are close to the philosophical conception of God.
But there is no proof that the world we experience and see is “being” that requires explanation. That is just a baseless innate assumption.
“No man can see Me and live.” One cannot live without change.