.
It's best to include it naturally in a post. But if you can't, you can send a PM to an account that won't delete it (you could use
DefaultTrust for this). After you send it, check your outbox and make a note of the PM's ID (visible in the quote URL).
Add it to your signature and the bitcoin address section. Even if the hacker changes it, theymos can check.
I can't conveniently check signature edits.
I think you're supposed to send it to yourself in a PM
I can't conveniently see PMs if all recipients have deleted it.