The Javascript editor chokes on the following characters:
*, $, \, [, ], ^, ', ", {, }, \
I'm sure there are others, but those are the ones right there on the keyboard for me to test. Some of those are obvious and not bugs (' and ", for example, are used to provided title text). I could test the server-side Markdown processor, but that'd be difficult and unpleasant.
The original wmd editor doesn't appear to have these bugs, which implies that it's something in the showdown engine. I would imagine the server-side version was designed to mimic the preview editor as much as possible, which would explain why the bugs persist in the rendered posts. That's just a guess, though.
