I've got a problem on one of the sites I manage, http://www.thewritingpatch.com, with the spacing of the iframe in which the Jetpack comments box is loaded from the wordpress.com servers.
As you can see from the site, I have the comment box positioned above the comments, and the comment box should (as in all Jetpack installations) expand when clicked on. However, on occasion when the page is loaded, the iframe does not collapse initially, and instead there is a large amount of white space under the box. When the box is clicked on, this space disappears. I have uploaded screenshots to illustrate this effect:
I have witnessed the problem in Chrome, Safari and Firefox on Mac, but it does not occur every time. I would love someone to help me pin down why it is happening so I can eliminate it and use an otherwise excellent comment system!