With the Steam release incoming, we're probably going to get a lot more activity in the existing chats. Giveaways and Trade are already pretty busy too, and have a lot of off-topic chat even with the revised Trade Guide. I think we could do with at least one more tab to move things like fruit conversion and price checking out of Trade, and possibly another general chat alongside Global and Spoilers to handle a larger volume of active players.
Additionally, as this would make keeping up with chats more difficult, I'd suggest reworking the ping system a little, and having each chat button light up with new messages (configurably), as well as having a new colour to indicate you've been @ specifically in a chat. This would mean people could post their WTB/WTS in trade chat, tab out to have off-topic or general chat, then pop back in when they see they've been pinged.
