I have successfully hacked the chat module in Moodle 2.5.2 to use a textarea of 4 lines, with a vertical scroll bar, and a separate Send button. It may not be perfect yet, but if anyone is interested I can send them the changes which are localised to two source files.
multi-line input to chat
Great work you have done there! This is just what the doctor ordered for a key improvement to the Chat module. Kindly send me the details of the hack. Thanks for sharing. One more thingy, I'd love to blog about this on MoodleNews.com and on my blog at http://moodurian.blogspot.com. Can this be made public? You'll get all the credit for the hack of course!
Email me at email@example.com
Moodle + Durian fruit = a slice of heaven