What percentage of an Editorial Letter do you realistically expect an author to accomplish? Or, better phrased, how often does an author fix EVERYTHING you claim is "wrong" with a YA/MG novel? If you disagree with the author, that this certain thing needs "fixed" and the author thinks it's fine, who wins? Who ends up crying? Are any broken bones involved?No, broken bones are for when you're in breach of contract. Editorial letters are only a matter of sprains and bruises. See, if you don't solve my "problems", we have some "friends" who come over to your house to "explain" things to you.
But seriously, here's how I recently answered a similar question over at the institute:
What I want from my authors are:
1) to consider my suggestions seriously
2) And if they don't agree with a suggestion, to consider if there is another solution to the problem I'm trying to address in the manuscript.
3) If they truly disagree that the part I've marked should change at all, then I want them to show me they've seriously considered both the change and the issue I was trying to address, and to tell me why they think it's important the way it is.
As long as you do these things—which show the editor that you take her contribution and her book experience seriously and are willing to have a reasonable conversation about edits to the book—I would be happy. It is, after all, your creative work, and if there's a place where I'm not understanding your creative vision, then please, try to talk me around. Sensitive, open-minded disagreement is a VITAL part of the creative process. Your editor is offering you this. Offer it back to her.
I suppose I should also say something about the occasional Deal Breaker. Every once in a while, an author wants to do something that I feel significantly hurts the book's appeal to its core audience. Of course, if I see something like that at the acquisition stage, I'll make sure the author and I agree about the necessary change before we get to signing a contract.
But if something like this comes up later in the process, then I try to be very clear that's what I feel is at stake—and if the author and I cannot agree, it will be part of my responsibilities to my publisher to take the matter to a higher authority... in which case the book may be canceled. It's not fair to my publisher for me to continue with publication of a book that I believe has cut itself out of any audience.