I might not be thinking broadly enough here though.
A domain in this case is akin to a hash of a public key, or something like that, just enough to securely identify the target of the communication so there’s nothing to “revoke” although that’s not to say the peer discovery systems could not try to blacklist you.
Decentralized DNS with human readable addresses (unique screen names) is perhaps more a political problem than a technical one, and hence never fully “solved” just different sets of trade-offs that can be made.
However, between these two you can only pick one. You can't solve squatting problem without some kind of authority over issued names.
Careful with those words. Experience taught me that if there isn't a reason to ever want to do that, reality will eventually provide you with one.
There's no reason to ever revoke control for messaging systems, though, genuinely: imagine if your e-mail address could be taken on a whim by anyone. It can be! But you'd never want to revoke control of a domain rather than just marking it as spam or illegal and dropping messages from it. It functions as an inbox more than it functions as an outbox.
Addressing space should be permanent.
Especially given in an environment like this it'd be used mostly to get the initial connection, performance probably wouldn't be too big a problem.