~username has generally meant "a folder belonging to username". In non-threaded discussion boards, and I believe some older message boards @username was used t

~username has generally meant "a folder belonging to username". In non-threaded discussion boards, and I believe some older message boards @username was used to direct a particular portion of your message at a specific recipient while still keeping the message public. I keep seeing lots of hate for the proliferation of "twitter's" @mention syntax, but its use predates twitter by a loooooong way.