The actual reason why self voting was not banned from day one, is the very flimsy argument that you can just create alts to do this, or you can buy them, so, why not just let people do it directly, since they will do it anyway.

Then the entire platform is flimsy (which I don't believe is true). If you want to combat sybil, you will have to invent a whole new technology: Cryptographically verifiable unique identity

I'm not saying this is impossible. But, like I said, it's a whole new technology. Actually, I wouldn't be surprised if someone wrote a proof to demonstrate one way or the other.

Sorta like the halting problem. It's mathematically proven that the halting problem cannot be solved. But you can set bounds to side-step the proof. So even if unique identity cannot be supported by a proof, there might be reasonable bounds.