A useful site setting would have a separate designation or button to click to make a WTB ad. That way new members could be locked out of replying to them or even seeing them. The sentiment is don't join and then immediately go straight to selling parts. There's more than one spot on the internet to sell stuff. New members could also be blocked from contacting other members privately/through their profile. If they want to communicate with someone then just reply to them in a forum discussion.