Not exactly sure about what you mean by ''signature on these handy dandy forums.'' Anyways, if you mean ^ like how I did ''Meep'' or how Bopp did ''you can't?'', then you can easily write a worded 'signature' in the subject line whenever you comment.
I am not aware of any signature feature built into these forums.
Perhaps you could write some kind of external software to automatically paste a signature when you post here. Perhaps someone has already written one.