What does this offer over a place like twitter where the exact same conversation is playing out in public right now?

You can use the distributed proof to say that these accounts belong to you. So if you are doubtful about the integrity of a post, you can look up their blockchain ID and find out what have they been doing elsewhere publicly. Additionally, any post that does not attach a blockchain tag or something will simply get filtered out or ignored. This puts every "anonymous" post on the web a weight which it does not have in the age of LLM.

How are you guaranteeing that this ID corresponds to a real human bean? Blockchain seems terrible for this on the basis of complete reliance on an external central authority.

It doesn't but you can always augment your ID by attaching a government ID or some sort. On the internet tho? If you _only_ have texts, there is no feasible way to distinguish a person and a bot.

And how would blockchain mitigate this?

Isn't blockchain a kind of distributed proof? You can now say that this user in reddit is related to this post in hackernews via blockchain. Of course, there's no way to prevent a bot to create multiple accounts in multiple websites but I am to understand that there's a cost to this.

OK... I'm not understanding what that would solve, though. That addresses people posing as other people (and you don't need blockchain to do that), but doesn't address identifying AI commenters.

You can always augment your account with your government ID or some sort if you are famous.