I submitted a much shorter novel excerpt, reframed as a short-short story, to two online magazines. Same story, from one, a very polite but note-free rejection, and from the other:
Thank you very much for submitting work to _____________. This piece isn’t right for the magazine, but please keep us in mind for other pieces. We are interested in reading more of your work.
My question is, are these notes meaningful? Do they mean, straightforwardly, what they say?
Thank you for submitting ________ to __________. Though your story was given serious consideration, I ultimately decided not to select it for the upcoming issue of the magazine.
The only way to know for sure is to send some truly horrible writing to the publications that sent you the encouraging notes, and see if you get the same responses. I've seen form rejections similar to the second note. "Your story was given serious consideration" doesn't mean it was given more serious consideration than other stories; literary magazines like to think they consider all submissions seriously. Note that they not only decided not to select it for the upcoming issue, but did not hint that they might want it for a future issue.The first note, on the other hand, is unlikely to be something they say to everyone. The last thing Evil Editor would tell a writer is that he wants to see more of his work--unless he actually, inexplicably, did want to see more.
Of course they're hoping that if you send more, it'll be right for the magazine. Apparently it's up to you to figure out why the first submission wasn't.