Um, nevermind. I found out that the posting box width/height is customizable by the user. Although I'd suggest changing the global default to 60/15 instead of 80/5 so that new users aren't bothered by it.

And the "New message" bug probably isn't something that can be edited by the board administrator. It's probably a bug in that version of wwwthreads. Perhaps an upgrade to a newer version of wwwthreads would fix it?