I think one of the things that killed many forums was cluttered layouts. At their best, signatures we're like catchphrases or ads that you attached to your account. At worst, they could be overly distracting, break up the flow of threads, and possibly break the page itself.
I think one of the big reasons sites like Reddit took off was due to it's simplicity. All you had was the comment, and you could easily follow conversations since they stacked and weren't cluttered with distractions. Compare that to a site like Gaia, where users could put practically anything in their signature, and made scrolling through topics a nightmare.
Keep resetera clean please. I don't need to know how much a user loves Boba Fett everytime they post.