I have no idea. But I would assume they would comply with the law in order to not get sued?
One person made the extension. It wouldn't take much for a company to threaten a lawsuit to take the extension out of operation.
Yup. That's why I don't post my SSN everywhere. A single data server with all the comments without any moderation won't survive. But a group of data servers with different rules and many entry points via extensions or websites, can survive.
> give any party the power to unpublish not-legally-allowed content
Like the party that published it?
Yep, it's possible in theory. Comments are signed with ed25519 and the author can sign a request to delete the comment.