I agree, Sunnie.
The huge downside of allowing puppy sales here is that many people, especially newbies, mistakenly believe that the breeders who advertise here are screened and recommended by YT. Newbies are regularly referred to the For Sale section when they join and ask how to find a reputable breeder. I doubt many of them read the disclaimer in the rules.
Comments on sale ads could save a potential buyer from making a huge mistake. Of course, all comments should be polite and educational rather than just personal attacks.