The posting editor in the ACP / Users / Signature needs fixing.

First, under normal conditions the color palette looks a little weird (there is a 3px padding-top to it which is extending some of the border-right to go above and beyond the color palette).

But mainly the responsive design goes bad when sized down. The text area gets pushed all the way down to the very bottom of the page, all the way at the bottom of the color palette, instead of staying at the top with the BBcodes.