Put "..." or something similar above someone's head when they're typing into the chat window. This way, if you start a conversation with someone you can tell if they're typing back at your as opposed to being AFK or just ignoring you.
It would only work for IM's and maybe not even then, but I like unix's "talk" where you can see what the other person is typing as they type it. Conversations go twice as fast cuz you don't have to wait for them to finish the sentence or edit things just so.
Maybe it could be an option for the player? While I can leave mine off, you can turn live typing on, and, that person over there *points at a random person* can use the ellipsis.