You both have valid points, but I am afraid the 'solution' would not be enforceable. Similar to posted rules for Auctions, and before that for Raffles, the admins can enforce certain rules for Classifieds, one of which could be that ALL dibs have to be first posted in the ad, then followed by a PM. This way there is never a dispute about the hierarchy of dibs and who
should get the chips. But who should get the chips and who will end up with them are very different, even if you have the first dib.
The reality is that several prolific buyers of higher-end chips don't like to express their interest and eventual acquisition of certain chips via posting in the Classifieds. And some offer a higher price via PM, and the sellers decide to sell at the higher price. Lastly, just because someone thinks they have dibs on chips, doesn't mean they will get them, or are entitled to get them. There are several members that I will never sell any chips to, regardless of how many 'dibs' they post in my ads.
Lastly, I hardly ever see members posting negative reviews, despite the fact that some truly deserve it. Maybe there is a better mechanism to alert members of less than honorable dealings, rather than staying silent and leaving others to experience it for themselves.