Constructive, interesting, funny or descriptive comments, rather than damp unenthused comments that sound like they have come from the mind of a man who has been tied to a chair whilst Rockmage receits his lifelong works.
A good example of the commentry I am talking about is given on count all the stars by dancingshamrock:
http://poemranker.com/poem-details.jsp?id=134711
(There is a number box to tell people whether it is good, bad or mediocre)
I deleted the comments after a rewrite, they were of no use. I think it was along the lines of "Allright, sounds like a metallica song". I just think that something a little more constructive may help you and the recipient yield more from your commentry.