I think it would be nice to see when a user goes AFK (or comes back from AFK) in a similiar fashion to when they join or quit (or do a /me).
So I type /activity AFK , to go offline and a status message appears in chat:
Baby Bonnie Hood has gone AFK

Why?
Upon joining the chat you are usually greeted by other members because they see the status message: Username joins Hyperspace Chat
It would be nice if you could get the same thing when comming back from AFK don't you think.
I say this because I've noticed that a simple "hello" upon comming back doesn't activate the same response as you would get if you reconnected (refreshed the webpage); people get confused, wondering who you are greeting when no one actually joined or left the room.

Gosh now I sound like some person with Histrionic Personality Disorder or something but that's not the case I came to think of this because I've seen it in other chats (don't you have AFK -status notifications on IRC for example?).

It's a worthy idea.