Yeah. Thanks for bringing that up. I think the main issue once relays start banning people for their speech is alternative relay discoverability. For example, if the sysop of nostr.band bans me we wouldn't be able to communicate since it's the only relay that we have in common.

It would be nice to have an immutable list of relays that currently exist. Probably something like the PGP keyserver protocol where a sysop can submit their relay address signed with their npubs. The keyservers can then share their contents with each other to make the records uncensorable.

That hypothetical protocol could also probably borrow the idea of revocation certificates to remove a old relay record in the server.