This is an old post, but I thought it would be good to bring it to people's attention again: The 8 Rules of Rejections. While all the rules are worth reading, I think rule #5 is particularly insightful: "Most rejection letters are a long, long way from direct, forthcoming, or meaningful."
Now that I'd given up day-to-day editing at storySouth, let me confess that submission editors don't want to go into great detail on why they rejected your story. We didn't like the story. That's all that matters. But we don't always say that. Maybe we don't want to hurt your feelings, or we want to encourage your writing. Maybe we like your other stories and simply think this one is poo. Or maybe we think you're psychotic and don't want you tracking us down at our house. So we reach into our bag of pleasant banter and tell you pleasant words to mollify you.
Such is life. But this is why it's never good for a writer to obsess on what a rejection letter says.