It's extremely complicated and I don't really see a solution.

You'd need gigantic resources and trust in those resources to vet accounts, comments, instances. Or very in depth verification processes, which in turn would limit privacy.

What I actually found interesting was bluesky's invite system. Each user got a limited number of invite links and if a certain amount of your invitees were banned, you'd be banned/flagged to. That creates a web of trust, but of course also makes anonymous accounts impossible.