It has something to do with your "show signature" box being off by default when you have no sig, and turns on when you do, so that is why.
It will show up for you in all your new posts. Enjoy.
All good. I like it, I have no clue how to make them and am clueless in PS or whatever people use to make them so coming and asking was my only hope.
Edit: Ewww almost forgot to credit you on it, that would have been embarrassing.