A real 'block' option would be nice on the threadiverse. Right now all we have is a glorified 'mute' button. A block, to me at least, implies that the blocked person can't see or interact with my posts or comments (and not simply that I can't see their posts/comments).
It might complicate things if people who block each other post the same link to a community though. And I assume that federation likely makes implementing this more difficult as well ... but still, it would be nice!