> a distinction should be made between restrictions (on speech) by government, and restrictions by private entities. The former is dangerous, the latter is necessary.

Both are both. There is no country (AFAIK) in the world where there are no restrictions on speech.

I think another distinction needs to be drawn: Moderation of communities that is organized and controlled by the community is structurally different from externally imposed rules and standards.

There are structural power issues with the latter that need to be acknowledged and which should lead to to try to limit it where feasible.