I don't rate using a number system because it encourages you to type without thinking about what you are typing. People rate, and then forget to evaluate or discuss. And if you do both of these well, there is no reason to include a numerical rating. Ratings are great for statistics and gathering an idea of which builds are popular, but the sort of "showcase your artwork" setting of the gallery, I don't think they are really appropriate. There isn't a way to sort by ratings either, so rating is pretty much useless.
It makes your post seem more authentic and personal when you don't try and quantify artistic talent. To follow up on that statement, I've never seen an art journal say something along the lines of "Mr. Ensor demonstrates excellent use of contrast in his latest work, it gets an 8/10."