Is there any way to prevent someone posting in Buy/Tade/Sell based on having less than the required posts, or on length of membership?
That would be Rammstien. But posting spam is a violation of that forum's posting rule so they get banned when they do it.
I could with posts, but the spammers will just post in other forums. It just so happens that it was the buy/sell/trade forum the most recent time. However most of the time they just post anywhere. I have now started banning the ip address of the poster. If it keeps happening, I will start contacting their Host and reporting them. If the spammer is in the US, they can get into legal trouble. If it is overseas, I will just block their host's entire range of ip addresses.