The physicsforums.com message board annoys me by having too-small of a box in which to enter messages. It is 540px wide, which is way too small on a high-resolution screen. px is evil! The suitability will depend on the font size!! I would normally just resize it using the text-area resize add-on, but it is centered and that doesn't let it move left; also the other annoyance is the animated "smiles" panel to the right of the text entry area.

This script will delete the smiles pane, remove the hard-coded px ref, and re-layout to let the "reply" form size itself to the window.

The message board uses vBulletin 3.6.7 PL1 by Jelsoft Enterprises Ltd, and I tested it with the "PF-Prime" (default) skin. This may work on other message boards that use vBulletin. I don't know to what degree the output is customized for each client. If not, it would serve as a good starting point.

Updated: widens the "Quick Reply" box to 80 characters, applies to Private Message sending, and works with vBulletin settings that don't have "smilies" pane turned on in the first place.