I think it would help sales, as it would give people an reasonable idea of what their names are actually worth, rather than their inflated expectations, and cut down on people posting awful names for sale, as they will be ridiculed, this in the long run would make the sales threads more interesting and improve the quality of the names posted for sale.
When I joined this forum in 2005, I learned a hell of a lot from people posting in my sales threads, and from the appraisal section , but these days nobody gives appraisals, as most of the names are not worth appraising, and if people do appraise most don't like what they see, so just get shirty.
Some might say that a potential buyer could drive down the price of a name by devaluing it via their comments, but I believe that most established members on this forum are honest enough not to do this, and weed out those that did.
Of course there are difficulties with this, as alot of the time it is a matter of opinion, and the old 'It's worth as much as someone is willing to pay for it' but there are obvious cases where the names posted are awful and overvalued, and it's in these cases that I feel the member should be given a lesson in domain valuation.