I agree that initially it really looked like a z-index problem but this is why Firebug is so cool. It lets you play with and adapt the live CSS in your browser, so I was able to pull the comment bubble upwards and have a good look at it away from the overlay. That’s when it got obvious 🙂
Try increasing the height of .commentscap to 36px. Then add position:relative;top:6px;.