I just have a couple of suggestions that I'd like to see in chat. I know it might not be possible or widely wanted so see what you think.
'is typing...' common in many forms of chat but very useful here as you can anticipate a message. I noticed something very subtle like: if you're in a private chat and you see the user icons switch it means the other person is typing. But it's way too subtle and easy to miss.
SEEN - due to there sometimes being no indication if someones even joined your private chat it would be nice to have something. SEEN icon would be good. Maybe even if they click you off before looking at your message it could change colour on your end so you know what happened. Sometimes you just wonder, you know. Which brings me to...
Status - sometimes you have a few conversations going and something crops up. It would be good to just change status to let everyone know you're away from your computer for a tick.
I can't have the sounds on because of the constant racket but I'd love to turn it on for private chat notifications only.