Generic teacher end comments?

In response to Summer Smith's article about the genre of the "end comment," I find that I have to agree with some of the points that she raises about the generic characteristics of some comments that teachers use to evaluate student writing. I've seen this on many of my past papers, comments where teachers don't really say anything of substance except "improve" or "good job." I find that this does not help my writing improve because it does not give me clear indicators of what is actually wrong or weak in the essay. However, there have been many cases where I have received great feedback. The best feedback I have received on a paper focused on the originality of my argumentation and how well I used the supporting evidence to prove it. It was the teacher telling me whether or not I had convinced him of my argument and my grade based on how effectively and "eloquently," as he put it, I had succeeded in doing so. I do feel that some professors need to break out of the genre of end commenting in order to truly evaluate student writing rather than simply skip around the issue to avoid problems with offending the student or problems with the institution that might arise out of offending a student for criticizing his writing. I personally welcome criticism in all forms (as long as it is justified), and it is very useful when teachers are actually honest and specific rather than vague and conformist.