There are some mantras common among editors.
Do no harm.
Put readers first.
It’s not my book, it’s not my book, it’s not my book . . .
The goal of any editing job should be to help the author tell the best possible story or to send the right message or to give correct information in a way readers will understand and appreciate. Other than that, less is always more.
Style guides and dictionaries document how the speakers and writers of language use that language. Those reference texts are meant to help guide us in our editorial decisions by offering prescribed rules and meanings for language. But just as there is a time and place for prescriptivism, there are times where it is necessary to bend those rules for the sake of conveying intended meaning accurately and authentically. Descriptivism is when we allow for nuance in language use—when we allow for the realities of how people actually use language in real life, rules be damned.
And yes, we must serve the readers first whenever possible, but it’s the writers (or publishers) who pay us and who are in charge of the copy. It’s their message, their story, their narrative. We simply help writers sift through the silt of words filling their manuscripts so that everyone can see the gold there.