Fediverse

there are certainly ways to solve it, like having the vote identity split between multiple servers that can still confirm with each other that the vote is valid, but neither would reveal the actual identity to make it traceable back.

This doesn't solve it. I can still just make multiple accounts and vote multiple times.

The only way to solve it would be to actually verify that each account is associated with 1 real life person and then verify that each person only votes once on each post. But that requires essentially verifying a passport and documents for each user which is totally infeasible and has far worse privacy concerns than public votes do.