I would think a reasonable solution to the situation would be to create a temporarily-stickied "Post Here!"-like thread in the "Free MMORPG" forum or perhaps the aeria game forums, that promoted these individual spammers to post
in the thread, as opposed to anywhere else.

Perhaps in the thread you could also dictate a rule that suggested you will get banned for posting somewhere else.


Hope this might help.

(edit: or perhaps a more sheep-friendly "Promote your aeria game here!" title)
(double edit: oh, just noticed the "shameless promotion" section. well.. If I didn't notice it, spammers certainly won't.)