I'll just toss this idea out there. Why not a blanket, no posts of any kind in BST until 300-500 posts? Make the number way too high for it to be worth spamming, and do it problematically. Then you can also monitor the top posters of the day/week for the few that would try.
People with low posts can't ask for review copies, they can't hijack threads, they can't post dumb questions. You've instantly eliminated fake reviews and reviews from complete tards. Tards from wafo can't just storm in and paste their garbage. They have to stay here long enough to get up to speed on how we roll. Anyone taking the time to make 500 posts over a period of time isn't going to post rainbow scam text to only get banned in 5 seconds because they stick out now rather than blend in with 100 other garbage posts.
If noobs want to ask questions they can send PM's. If they have a bad experience they can leave itrader.
How many awesome service providers are there with <500 posts? How much more useful would the forum be if the front page was full of red_virus level service providers?