Respectfully, I totally disagree with your post. The only jackwads I see are the ones who want to decide what is best for others. Why is it so hard to let another member decide what price is correct, what he/she should buy, or what he/she should not buy? Keeping people honest, really? You honestly believe that profit was not made on this site before the present day panic? You believe that since you cannot post negative comments in another members ad, it will lead to posting negative PMs to that member? Do you really send negative PMs to other members because you don't like their price? Why? As for feedback, since you are not a buyer, there would be no feedback to leave. Your opinion of the price of an item is just that, your opinion. I do have a suggestion for you, find me one post started by a disgruntled buyer who was upset at the price he paid. All I ever see are non-buyers upset at pricing. Check the feedback score on the member who sold the item that you felt was a too high price. Someone must have liked the item enough to pay the price that you did not like.
I can understand what you are trying to say, however the comments in an ad (positive or negative) can be informative to the seller and aide them in deciding what price THEY choose to list an item for. Disabling the comments would just provide a blanket of security for someone that would otherwise face constructive criticism.
As far as the mention of negative PMs if comments are disabled. If that does not become a trend, something else will. This site is full of passionate people with an opinion. It has been shown repeatedly that through more rules, people evolve their way of voicing their opinion. Today for example, members received infractions for mentioning they rated the ad.
People will continue to voice their opinion and will evolve as they have to find new was to make that happen. It just makes more work for everyone trying to maintain civility. More rules= more infractions= more moderators= larger # of subjective interpretation and enforcement.