thats what the reviews are for. if your "comment" isn't good enough to be a review it has no value. just look at animenfo. those "reviews" they have are the comments you want and we need no "this anime sucks" or "this anime rulez!!!111" comments.
There is also a comment system for the specific group fansub/dvdrip to give some comments about their subtitles/encoding quality/editing/etc to indicate which are good ones or which seem to lack something or are just (not) recommended to grab.
