OK, is solved. I have a copy of ZingaBurga's mycodepack, and I added the bbcode in via that file rather than trying to use the MYBB MYCODE editor. I would appreciate a yes/no on how "safe" this code is, and if unsafe some tips on how to fix.
EDIT: I missed your post RateU - yea, its insane. That scraffly little mycode SHOULD have worked - but no go. This way is working - now I guess I have to add the mycode version into the post preview set up?
LATER EDIT: Muwhahahaha - it worked!! Yay. Thanks for listening