Please please please give us a way to style the h3 in the Jetpack iframe. What this would really require is simply moving the h3 out of the iframe so our own local CSS can take over styling. As far as I could see, this would be a backward-compatible move.
Alternatively, just give us a way to HIDE the headline altogether. For example, simply leaving the "Greeting Text" blank could hide the iframe's h3.
Either of these approaches would make a world of difference in integrating JetPack comments into themes.