That could be it, though from my experience post count or join date shouldn't matter much, scammers wills scam, they'll open an account, post a few comments and leave the account inactive for several months then goactive before putting something up for sale, but i understand what you're saying.
If anyone is a member at photography on the net, they can look up my username there. I have 3 pages of feedback and has been selling there for 3yrs.