An idea:
Some users have troubles posting preformatted code or ASCII art.
What about a "Leave formatting" button, which would leave the text formatted as typed in into the edit window (unparsed and with the same font; maybe even wrapping at the same size as the edit window is).
Not my idea, have seen it somewhere.

Similar idea:
Make the list of "Acceptable HTML Tags" clickable, so that it inserts the according HTML tag into the edit window.

Jan Waclawek