Those problems affect not only opera but Mozilla and KHTML based browsers (I haven't tried any other agents yet)
The code tag bug is a major issue. I would do the following to the BBCode for the forum:
change [code] tag to interpret as plaintext if the browser agent is read to be anything but IE (and compatable version at that -- i haven't tried any old versions). the plaintext html tag will line up characters in their respective place so it still "looks" like code.
