The arrow key navigation in the gallery is ridiculously annoying if I'm trying to edit a comment. Please do not listen for arrow key presses if the comment text field has focus.
I do not have this problem on any browser I have and I made a special point to disable navigation while in the comment field, which is why it's marked as complete. What browser (and version) are you using?
I too am still seeing this bug when in "Edit image titles and descriptions" view. I see it in both Firefox 7.0.1 and Chrome 15.[mostrecent]. Left arrow and right keyboard keys, while moving the cursor within the description text you are editing, also causes scrolling all over the place.
Additionally, FireFox also appears to have a bug where the "Title" and "Description" textareas don't respond to clicking to let you move the cursor where you want.