On talkpost.bml, if you put any BML in the textarea box and then choose to preview it, talkpost_do.bml will parse it without escaping it. In fact, you will see the bml twice, because one of the hidden variables in that form will be the message body (which has the BML).
This isn't an urgent fix, because including "(=_CODE" doesn't work, but it is annoying when trying to include example BML (or for people that do weird emoticons, I guess).