I think this is part of what ATProto is trying to solve by decoupling identity provider, data provider, and labeling. That's not to say a million fiefdoms is n

I think this is part of what ATProto is trying to solve by decoupling identity provider, data provider, and labeling. That's not to say a million fiefdoms is necessarily a bad approach. A small server where all the members know each other is much more likely to be run in a way that's satisfactory to all its members than a big one. Furthermore, users have the option to maintain multiple accounts.