I give up. I give in. I concede defeat. Regular expressions have been for a long time been my weakest field, and my attempts to make a Java version of Textile have ended in ignominy.
Has anyone already performed this regex-a-plenty task? Or is anyone else willing to give it a go? Go on Lazyweb, be my hero.
(Mark Pilgrim also wrote a version in Python, which you can see here)