Dunno. But it shouldn't be fitting the screen anyway; at most it should be extending to the edge of the beige background of the "post reply" section.
Interestingly, though I have the usual resize handle at the bottom right (this being Safari), I cannot use it to shrink the textarea horizontally.
If I change the "cols" value to something much smaller using the Web Inspector, I can resize it to the normal size, but I can't resize it smaller than what the "cols" value makes it. ...Not sure if that's normal behaviour or not, offhand.
