It's interesting phase on fediverse, not hard to be well-known right now. I've certainly remember some usernames from seeing them at unrelated communities in different instances and they're aren't even trying to be popular, just leave thoughtful comments a lot.

Thanks, very helpful! What about posts from instance B and comments in instance B post? I'm assuming instance B users can see both comments from instance A users and instance C users but for them (instance A and C users), they can only see their respective instance users' comments and instance B users' comments?