My wife frequents another forum site(a baby site of all the forums...Ugh) and they are given the option to turn off they're signatures on a post to post basis. what I think would be good is either being able to switch ya siggy off for the post you are currently writing or being able to turn it off for that thread only.
It's there when you Reply at the bottom ! [bold][]Check this box, if you want to use your signature. [/bold]
Jeanc1 read my mind. though i use the other tickbox a lot when i teleport threads to relevant forums, and have no interest in the thread itself so i get to unsubscribe before i subscribe so to speak. it's underneath that tickbox