At the moment the server owner effectively 'owns' magazines & communities. Is that the right balance of power? What happens when servers go offline, or server admins go rogue?

In a world where both users and magazines had public and private keys and magazine moderators had the tools to do off-site backups.

Could the magazine moderator then do an unassisted migration to a new place?

They revoke the key that gives the original server the right to host the magazine. They use the key to re-create it on a new server.

Somehow notify all the members the magazine of the new location. The users use their public keys to reclaim their identities and content.

Would that give mods too much power?

It all gets complicated fairly quickly! I think the Bluesky AT protocol is somewhat close to this model for user content, but doesn't really extend to 'community' scale content.

It falls short of a full confederal protocol