The only way this works on HN is through active efforts to remove some of the anonymity -- I'm not talking about actually finding a contributor's real-world identity, but making sure that the same person doesn't create 5000 accounts and just switch to the next one when one gets banned.

This requires at the minimum logging IP address that someone signed up from, and treating with suspicion IP addresses that are pooled (such as from a VPN or TOR, etc). There are also other heuristics to prevent sock puppets and voting rings, each of these removing some amount of anonymity.

Whereas what i proposed, people can still maintain full anonymity, and if they really need a separate ID so that they can log in to the same forum under a different ID than they normally use (for things like whistle blowing, etc) then they have that option -- just buy another $5 (or cheaper, or more expensive) certificate.

It would be up to the forum (or the auto moderation system, for assigning points), to decide how much to trust a user with a new cert, based on how much they paid for it (as an example), or how much PII they provided to the cert provider.

Another thing this can do is allow someone to be anonymous, but with a chosen pseudonym, and allow their reputation from one site to benefit them on another site (by proving that a given reputation score belongs to them). Of course, this is almost sounding too much like a "social credit score", so it may not be acceptable on those grounds.