@forteller
Unfortunately you can't remove them entirely, but:
* They will no longer be visible to other users on your server
* A server that hasn't yet fetched your post won't see replies from blocked folks (does not apply to domain blocks, which are actually more like "mute" in this context)
It's a little more complicated than that even — servers can also make replies from blocked people disappear later for other reasons — but the bottom line is that blocking those people *does* reduce their visibility on any past posts, even on remote servers.
For instance, I can't see any replies on your post with Radcliffe from any account I have right now (including half a dozen placeholder accounts on various servers)