As a thumb rule to commenters, the lower the rating, the more elaborate your comment should be.
I think it's a polite and a logical way to approach it, as it's quite obvious that if you're giving a track 9-10 score, there's really not much to comment apart from how awesome it is; it's fine to drop a vague one-liner on a track you find that good. Problems arise with lower scores as especially newer trackers would probably find it incredibly helpful to know why they're getting rated low by the commenter.
I've gotten trolled by one-line 1 rating comments too (I think Beyond was drunk) and I can say that if that happened when I wasn't confident in my music and was still looking for feedback/validation, it would've felt really bad to not get any explanation for the low rating.
And obviously no matter how bad a track is, rudeness and/or insults are still not justified.