[eqvinox]

That's not particularly useful without a reputation system.

In particular, any federated identity provider has a problem for this use case in that malicious actors can simply create their own domain - or multiple - and spam/troll from those. Blacklists essentially don't work as long as new domains can be created, so you end up with a whitelist, which kinda counteracts the federation concept.

It needs something where getting blemishes on your ID is actually something you want to avoid. And where fresh IDs is not effective to bypass this.