24. Advertisements (including signatures within the post area) in posts aren't allowed unless the post is in a thread you started and is really substantial and useful.[9][e]
We probably need to be on the lookout for this kind of behavior actually. As more and more spammers get banned and restart with newbie accounts, some may resort to this tactic when the realize they will struggle to get that one elusive merit.
Everyone who does the sig in post thing gets banned normally.
What is dofficult is when its more difficult to spot. Spmerimes it can be let go but advertising in threads outside of the economics section isnt allowed for the most part.