Currently, the sigs on the site are tied to the post. That is, if you make a post, your sig gets appended, then if you change your sig in your profile, your previous posts retain the previous sig.
My question is this: Should posts retain their sig, or should updating your profile change the sig retroactively.
Myself, I've always been partial to the "sigs on post" thing for historical purposes, but I see and understand the desire to be able to retroactively change sigs.