Okay, so if you want to have a signiture and it's not showing up, here's what you need to do:
Click on "Profile" under the header at the top of the page
then click on "preferences"
scroll down until you see "Always attach my signature"
and make sure you have selected "yes" to be your answer.
It automatically selects no and then never puts it on the post. Ever.
It's so lame.
It was so easy once I discovered that in the profile area. I didn't even remember seeing that.
So make sure you've done that and it should work.
I think for most people who wanted sigs but couldn't get them to work I went in and changed it already, so just make a post somewhere and see if it works.