Hello - a quick update on behalf of the dev team.
The backstory: Forum sigs are one of the extra features we've had for quite some time in our local development versions of the forum. Sigs were never released, as we weren't 100% happy with the them, both visually (see the big gap between body and the signature) and especially functionally (option not to display them), not to mention they aren't the top priority either :)
Fast forward to today: with yesterday's minor update we've accidentally pushed this feature to the live servers
without us noticing until late in the evening (or this very morning, in my case :). With other fixes to be applied, forum sigs will be pulled back for now until they are ready for the prime time.