There's a new (I think) feature on the box for leaving a comment on feedback: it automatically expands to match the height of what you're typing. That's pretty cool.
It's a little buggy though. In Chrome, there's a small one, in Firefox, a more pronounced one.
The Chrome bug: when you type a letter, the page scrolls to the bottom. When you hit a newline, the page scrolls to just below your new line of text. This results in the page jiggling up and down several times in the course of a post, so should probably get tightened up at some point.
In Firefox, the behaviour is different and the jiggling becomes pronounced and really bad. Whether you enter a new line or type a letter at the end, it scrolls to just below that last line. However: at ~10 lines in, it'll start adjusting to a pixel or two above that, and jiggling by a pixel or two every few characters. At each line past 10th, while I was typing, the jiggling was getting worse and worse, and another part of the page entirely seemed to be flashing into view for just an instant every few characters. It was awful to look at, and I would have moved to a text editor if my post hadn't been just about done at that point.
Also, in both browsers, it expands infinitely. If I'm on line 20 or so, the auto scroll to bottom will be enforcing that I am not allowed to have both the text box and preview in view at the same time. Maybe the box should stop expanding after line ~15 or so and simply let the scroll bar kick in.