On version 0.19 you can block instances so that you don’t see any posts from that instance, instead of having to block communities one by one, you still see comments from users of that instance in other posts so it isn’t completely blocking the instance.
None right now.
I block communities, not groups of users. I usually don’t have a problem with the actual users on an instance, I mostly just want to avoid porn (I don’t use lemmy for that, nothing wrong with it, though)
The only instance I would block is Threads but my instance admin is doing that already.