Text radio chat can be scrolled with mousewheel. Only mousewheel will put it back.

[SMH]

Just discovered this while trying to read an old message in the text radio-chat. When it's open for text entry, you can use the mouse wheel to scroll the text back. (Very slowly -- seems an unintentional feature?) However, only scrolling the mousewheel the other way will return it back to real-time. So it's easy to get into a state where you're behind in the text you're seeing, not even seeing your own recent messages until they scroll by later.