Would it be a terrible burden to require that the first X (5,10,etc) posts for a new user be manually approved before hitting the public board? Is there such a feature in whatever software this board is using? This way it would save everyone from this non-sense. I've seen other boards take this approach and it works well.
And while at it, prevent people with less than X posts from posting URLs, as a lot of spammers do: "(Mr. 2-post) - What do you think of this advisory site: www.ShillAdvisory.com" "(Mr. 5-post - his alias) - It is great! I used it myself and made a lot of money!" "(Mr. 2-post) - Hey, thanks! I think I will use them too!"