The game client is ill-suited to chat. The tabbed pane interface is a pain to flip between chats using, and it is probably the best possible interface for in-game chat.
The game client would be better suited to a social graph based updates system along the lines of what we see on our home page. These updates see a lot of use when the game is down, including some excellent conversations and question/answer back and forth.
The help channel could scale if presented this way. New players would effectively post "@help" updates, which could then be directly responded to by older players following the "@help" update stream. the "Help Feed" could also post hourly or half hourly tips on how to play the game.
There could be a few official feeds like this. Help Feed, News Feed, Developer's Feed etc. etc.
Groups could also have feeds, controlled by administrators, allowing them to make in game broadcasts to their members.
But mostly players would be seeing and responding to updates posted by their friends. Pretty much exactly like twitter or facebook, except in the glitch client.
Huge Advantages:
Feeds would all be merged together so you could follow *everything* on a single pane, or narrow down to a single feed to focus [or even something like twitter lists, eventually].
API hooks are MUCH easier to put into and use via a feed based system than they are in a chat based one.
Would allow "stagnant" groups to spark conversations without manually IMing everyone to purposely enter a chat room.
Of course keep the existing IM and group chat systems, which would actually be enhanced by this system, since "updates" could be clicked to initiate chats.
I think moving in this direction is probably the more important thing that glitch can do right now. If you see how well people are using the updates system outside of test sessions, and how well it is building community, moving the functionality and growing it makes far more sense than an unending series of odd kludges in order to make chat scale.