He rejected it the following day. And, true to form, his rejection was not gentle:
Thanks, but not for us. This was an "And it was all just a dream" story, ultimately, even if the dream had some medical import. When you have a cranky wallaby on the mantle in the first act, you cannot pretend that he never existed in the third. Also, the story was a bit unbalanced, as we as readers have many questions, but our first-person narrator apparently has none. It thus feels like a tease, especially all the material before the first scene break. That it ultimately WAS all a tease makes it so much more bitter a reading experience.
I was naturally a bit annoyed at first, because how dare he criticize my baby, but after letting it sit for a few days, I came back to the story, re-read his email, and realized he was exactly right. The ending was shit, and completely deflated the tension and weirdness that I'd gone to great pains to establish in the beginning and middle. He was right on the money to call it a tease, and I smacked myself in the forehead for not seeing it earlier.
So I heavily rewrote the ending, and tied it back to the rest of the story, and changed a few things around to make the whole thing more balanced. I believe this increased the word count by a third, as well. I then sent the story back out into the submissions ether.
The story, by the way, was "Strange Mammals," which was just recently accepted for Polyphony 7.
So, those of you submitting to Clarkesworld Magazine, don't be so quick to dismiss or try to argue with Nick's assessment of your story. You might get banned for one thing, but you're also missing out on really astute observations of why your story isn't working. (More of the same, and in further depth, can be had at a wickedly cheap price as part of Uncle Nick's Crazy-Ass Critique Service.)
Just yesterday, Nick offered a post on this very topic: "How to End a Story." Very much recommended, for writers at any stage in their careers.