It took me a while to find the "help" button for comments, and we seem to have a steady stream of people who have trouble finding it on their own. I suspect that's because it's floating off in a corner you don't have much reason to look at. Would it be difficult to move it to the immediate right of the "cancel" button, instead of the far right, and possibly rename it "formatting help"?
(I don't know enough python to look at the site's code, or I would check this out myself.)
I would never have known this feature existed if this post hadn't pointed it out to me. Put it next to to the "comment" button, and preferably make it bright red or something. (Ideally, it would be bright red UNTIL you'd clicked on it, and then it'd turn a less obtrusive color).