An issue, also in crypto, is that people will get their "identifiers" stolen. How do you prevent stealing, or recover stolen identifiers, without compromising anonymity?

Another issue is that people will hire (or enslave) others to effectively lend their identifiers, and it's very hard to distinguish between someone "lending" their identifier vs using it for themselves.

I've been thinking about hierarchical management. Roughly, your identifier is managed by your town, which has its own identifier managed by your state, which has its own identifier managed by your government, which has its own identifier managed by a bloc of governments, which has its own identifier managed by an international organization. When you interact with a foreign website and it requests your identity, you forward the request to your town with your personal identifier, your town forwards the request to your state with the town's identifier, and so on. Town "management" means that towns generate, assign, and revoke stolen personal identifiers, and authenticate requests; state "management" means that states generate, assign, and revoke town identifiers, and authenticate requests (not knowing who in the town sent the request); etc.

The idea is to prevent a much more powerful organization, like a state, from persecuting a much less powerful one, like an individual. In the hierarchical system, your town can persecute you: they can refuse to give you an identifier, give yours to someone else, track what sites you visit, etc. But then, especially if you can convince other town members (which ideally happens if you're unjustly persecuted), it's easier for you to confront the town and convince them to change, than it is to confront and convince a large government. Likewise, states can persecute entire towns, but an entire town is better at resisting than an individual, especially if that town allies with other towns. And governments can persecute entire states, and blocs can persecute entire governments, and the international organization can persecute entire blocs, but not the layer below.

In practice, the hierarchy probably needs many more layers; today's "towns" are sometimes big cities, states are much larger than towns, governments and much more powerful than states, etc. so there must be layers in-between for the layer below to effectively challenge the layer above. Assigning layers may be particularly hard because it requires balance, to enable most justified persecutions, e.g. a bloc punishing a government for not taking care of its scam centers, while preventing most unjustified persecutions. And there will inevitably be towns, states, governments, etc. where the majority of citizens are "unjust", and the layer above can only punish them entirely. So yes, hierarchical management still has many flaws, but is there a better alternative?