P.S., IMO the first-aid icon in the lower right corner of the compose window is confusing. I just clicked it and I still think it does something else.
away - when user is online but no activity for an X amount of time.
busy - set by user
invisible - set by user
This sounds like a good functionality to add to the chat/IM feature for NodeBB. The entire thing is due for a rewrite anyway, or at least the front-end.