Yes, I agree it would 'look' like you are condoning the sales but no more so than the want ad section and wouldnt really be an endorsement of ppl not listed. I understand though that some loopholes are not worth the trouble to jump through.
You are in a better position than I to determine whats an appropriate move to benefit ppl and still maintain the site according to rules set forth by your host.
But what about a sticky in the ad section then to point ppl to the scam lists already used?