Chat runs fast, and very often you miss a message. Scrolling back up to read it is a nightmare, because chat keeps updating, so it scrolls back down every time.
Solution: Do not auto scroll down while the user is scrolling up. It should only auto scroll when you are at the very bottom, or when you close the text box. If you scroll up, stop auto scroll. If you scroll back down to the bottom or close the text box, then enable auto scroll. Please!