In ticket body I enter this:

http://dl.dropbox.com/u/41764/tmp/Screen%20shot%202010-01-18%20at%200.44.41.png

The end result is:

http://dl.dropbox.com/u/41764/tmp/Screen%20shot%202010-01-18%20at%200.45.51.png

I can confirm that this is a bug in the Markdown renderer at this time. We are currently looking into a solution.