I don't see that you have to go to all that trouble. You still have the lines above and below the sig, even when there's no sig. The solution that lordtopcat gave was what I was looking for, editing it for the short __________________ above my sig. This is what it looks like on my site. Free and Custom vBulletin styles, skins, and themes - View Single Post - Thanks!
I've removed the top border of the second TD - which helps. See now how it's divided into two separate cells? I guess this will have to suffice.
I don't really understand what's going on but move everything into one td, remove the other td and place colspan="2" into the td you've moved everything in to.
I've revamped it countless times so don't go by anything I've previously mentioned in this thread. If you don't think it's too bad the way it is, we will leave it.