But what happens if someone gets your priv key and posts, "Everything I said before was a lie", or "was someone else"?
I suppose you could post the hash of a message that if you ever needed to *prove* it was you, you could produce the original message saying so, and nobody else should know it.
But that has the same problem of trying to prove you are you by keeping *others* from learning a secret.
I guess if the content of the message was such that it said something like "Only [My Real Name] can produce this message XXXXXX" where the Xs are crypo-salt.
Then it would be hard for someone with a separate identity to claim to be the account, they could only dox you.
