Nope. When you’re posting there is a Miscellaneous Options section below the Submit Reply and Preview Post buttons. You can uncheck the Show signature. But I was wondering if you could change it globally. Looks like you can’t.
Just skip the cleaning up. You can blame it on the quake. 
My beautiful sunny Saturday has dissolved into a thunder storm
Wait. Which one are you?
Just kiddin’. Nite D.
funny
Good nite!
Good night, LD!
o:o:o
Oooops. Neeevermind.
Yes, Spoon has already thought of this. He who is all knowing, Lord of frak-parties.
I knew you were going to say that. 
He is still my arch-nemesis, and he has thwarted me yet again.
I will avenge this wrong!!
I immediately thot of Lord of the flies, which is only fitting. No?
In what way?
Hey guys. I’m off to beddy-bye. I’ve been up too too late all this week. So 12:30 is nice early nite for me.
Nite all.
Good night, Thot. Good job. Sleep well. I’ll most likely kill you in the morning.
Good night!
Whyfore you kill him? That’s not nice!
Good night, TFG!
I think that’ll be it for me, too. G’night, all!
Great. Thanks. …Whut?! 
Good night, Badger!
Sorry, there’s a little Dread Pirate Roberts switch inside me, and it gets flipped everytime I hear someone say “good night”. Nevermind.