Dave, you are right that comments not directly related to the sale of an item are against the Guidelines. There probably are some abuses as you mention, but the moderators don't want to be too heavy handed in deleting posts that are more "fluff" than abusive. We'll try to watch more closely at any trend of collusive bumping. Fluff posts are another reason to not take post count totals too seriously.
From the For Sale Guidelines:
"Please restrict comments in this forum to those directly related to the buying or selling of the items listed in the topic."