I think some sort of rating system is a great idea. Major websites, such as Amazon, have customer review/ratings system. Commentary helps members make a better decision as what is acceptable to some, may not be to others. The general boards, and even some vendor sub-forums, are large and unwieldy. Many new members simply do not have the time to wade
through hundreds of posts, both informative and in some cases plain silliness, to find the information they need to make a good decision.
Simply allowing the vendor to delete comments is not effective. The member is not forewarned of service or product deficiencies because the complaint is deleted. The flip side of that is posts that are off topic or offensive are deleted and the vendor is made to appear to have an inordinate amount of deleted posts. The member may become suspicious that the deleted posts are indicative of a problem with the product or service when that may not be the case.
Even though there is a disclaimer, I believe, vendors enjoy a certain amount of credibility by their presence on this forum. It is an unfair advantage for unscrupulous vendors and tends to diminish the integrity of the forum. IMHO