Jay really started something with his blog posts, and it seems the discussion takes place on the blog. So I'll just add my two cents.
I like Jay's stories, they are easy to read, he has good editors, and I can't even comprehend why someone would say it was sloppy. Of course, English is not my first language, so I might not get the finer points.
Most people will agree that the mail he cited in his blog post sucked. It was in no way constructive, and it basically ended in a personal attack on the author. Nobody likes to get a message like that.
Jay says nobody here is a professional writer, and errors are to be expected. He's obviously right about that. On the other hand, his two blog posts gave me a mixed message. On the one hand, he says feedback helps writers grow and the stories get better. On the other hand he tells about a writer who stopped posting because he received valid and constructive citicism, because he was not interested in improving the stories. At least that's what I get from his posts.
So, should you send constructive citicism? In my opinion, yes. If a writer doesn't want it, all they have to do is disable the feedback system. If an author wants feedback but only if it's raving about how good the story is, that's not helpful in my personal opinion.
I'm happy about feedback that points out errors, because it helps making my writings better - even though it will never get to the level of Jay's stories. I'd like it even better if someone who believes they can improve the stories offers to spend the time to edit them.
Also, feedback is really the only way to know what people really think about the stories, the broken rating system is not exactly helpful.
What I don't want is feedback like the one Jay received, namely a message just to tell me a story sucks, and I should rot in hell for publishing it. I'm sorry you didn't like it but that doesn't help me at all. I also don't like messages attacking me for including something in a story the reader doesn't like, even though it's clearly noted in the story codes. It's not my fault the reader can't read, so why should I be held responsible?
All in all, thanks to those people who send constructive feedback, you are the reason I'm still writing and publishing my stories!