To be fair it's only the client (AppView) doing the banning, at least in these more talked-about Bluesky cases. If the banned user setup a DID and downloaded their repo they can get going again and still be indexed by the relay and viewed on another client. That's not to say the relay can't filter, but as of now it's only doing network level filtering and likely CSAM, etc. And maybe Bluesky will spin out the directory and there will be multiple relays in future, which would make it sort of poly-centric. So it could go either way, I think a year will tell.