> Requiring proof of identity is the only solution I can think of, despite how unappealing it is

Same. I agree that it is unappealing but it can be done in a way that respects anonymity.

I built this and talk about it here: https://blog.picheta.me/post/the-future-of-social-media-is-h...

I think we’re on the precipice of this being a requirement to have any faith you’re talking to another human. As a side effect it also helps avoid state actors from influencing others.