I can answer this question. We experimented last summer with having curators provide additional feedback to nominators about why a story was declined. Unfortunately, instead of increasing the quality of nominations, it only succeeded in increasing the amount of arguing from nominators, and had no impact on the quality of stories being submitted. As the person running the program (and a former editor myself), I really wanted the curator feedback to help nominators, but it simply did not work. Instead of improving nominations, it simply lead to more friction. Ultimately, we want to scale this program up to hundreds or even thousands of nominators participating, and having declined nominations turn into a debate simply doesn't scale.