Several people have asked for clarification on 'positive comments' in the classifieds being considered post dumping. Its been discussed and the rules in the classifieds have been altered to include this line: "Positive comments such as 'GLWS' are at the discretion of the seller. If the seller does not want comments unrelated to a transaction, even positive ones, they must specify it in the ad. Otherwise, non harassing comments are allowed. If a poster is unsure his comment will be viewed as harassing, dont post it."
So basically its up to the seller to specify if he/she does not want these types of posts allowed. Like said, if you aren't sure how your comment will be received, dont post it. Hopefully this answers all questions in regard to what is or is not 'post dumping'.
Thanks for altering the rule list MoT.