I know people are talking again about a distributed (blockchain-based?) forum preventing problems like this, and once that happens it will make "message forgery

I know people are talking again about a distributed (blockchain-based?) forum preventing problems like this, and once that happens it will make "message forgery" like this a lot harder. But a "low-tech" solution in the mean time would be for users to post a public-key under their username/account. Then when they publish a message, they include a private-key encrypted SHA256 hash of the contents of their post and append that to their message (in effect, signing it). Other users' client-side tools (say browser plugins) could pick up the hash, verify the message and indicate the message is authentic. Forging the public key or an already posted message would raise an alert for automated tools, other users and/or the poster. Would reduce the need to log all message contents, just the keys. Of course, does not prevent message deletions but that is under moderation scope anyway. Just a sketch.