Don't burn me if this has been mentioned before, but I am rarely on the forums, or the internet for that matter; except in CoH and for work. Thus, I haven't mined the forums for how many times this has been suggested before.
Suggestion: Reduce Local chat range to something like 20 feet and create a new chat called something like "Distant" which picks up the remaining range Local had before.
This would allow a lot of the open and private areas 'feel' larger and mitigate *some* of the chat-scroll. Just a thought.