What Strange Horizons really wants is a high-quality SF/F/Horror story. They see hundreds or thousands of low-quality stories for every high-quality story. And

What Strange Horizons really wants is a high-quality SF/F/Horror story. They see hundreds or thousands of low-quality stories for every high-quality story. And nobody wants to be told that the reason that they aren't being published is that their story sucks. But everyone sane can see that their story might have been done before, perhaps too often -- so it doesn't hurt as much to be told that your story is being rejected because it's on this list.