> First, the user knows this when joining a public community.

From Colibri: your community chats are public and visible to everyone by default.

So it's the same.

> Second, the moderators can choose to remove someone who has joined the community in bad faith.

Colibri has mod tools as well.

> Third, it is entirely different than broadcasting every single action taken by every single user in every single community on the entire protocol to anyone with one URL.

Sure, but then just don't use it?

It's really no that different from how IRC worked. Except persistent history is part of protocol and not some bots.

This is not public communities, not for small group of friends sharing edgy memes and discussing national security.