I ran up against the comment timer and its “Only 1 comment allowed per 15 seconds; timer reset. (click on this box to dismiss)” message and then proceeded to get stuck in the 15 second penalty box loop trying to guess when the coast was clear. It's very easy to get stuck since there's no indication as to when the timer has cleared, and since I have horrible short term memory I tend to try and add my comment before the timer has cleared, therefore continuing my timer hell.
I propose a visual indication, like a textual countdown timer or image, that clearly indicates when you're able to post another comment. The best place for this might be on the actual popup warning so that it doesn't need to clutter any of the site.