I believe that the signature feature was disabled some time ago. There was a problem with the way that search engines were functioning. If people listed gear in their signatures, which is what many people liked to do, then their posts showed up as search results. More often than not, the posts had nothing to do with the searches, so it was pretty frustrating.
At least that's what I seem to recall. People are encouraged to visit one another's profiles to pick up the info that used to appear in signatures.
There was more to it than gear listed in signatures screwing up searches. People were posting stuff that could be considered commercial, some negative thoughts, and trying to bypass the buy and sell board by posting items for sale in their signatures. It just was a smart idea to disable them.
