Editors are no exception.
Yes, we follow style guides that give us the basic (and not-so-basic) rules for how material is supposed to be presented. And we lean on dictionaries a lot to confirm spellings and proper usages of words. And we think about how our English teachers explained grammar and usage to us all those years ago. Then, once we have all of that in hand, we go out and apply it to what we're editing.
But, in the same way that we need to figure out the author's own style, we also tend to have our own.
A few examples:
- Current usage is moving toward "they" as a singular, non-gender-specific pronoun. Your editor has to help you decide whether that is right for your piece of writing and its audience.
- There is constant debate regarding whether or not sentences can end in prepositions. You and your editor should discuss how you feel about that. (Trust me - if you want to make that a hard-and-fast rule, you could end up with some pretty painful sentences.)
- Current usage frequently allows the pronoun "that" to refer to a person, instead of only indicating objects/places/animals/etc.
- Who is at the door?
- Who gave you that bouquet?
- To whom does this sandwich belong?
When it comes to usage within a sentence, though, it can get a little more interesting:
- "Who is the person that is at the door?" should be: "Who is the person who is at the door?"
- "Do you know the person that owns that?" should be: "Do you know the person who owns that?"
I can't imagine anyone saying "Who is the person what is at the door?" (Can you?) But again, in essence, that's what the "that" in that sentence is doing. It's making a person into an object.
Personally, I don't want to be an object - I'd rather be a person. And, when I'm working on an edit, I do my best to make sure that the people are people throughout, as well. (Unless... you know... it's part of the story where a person becomes an object, but that situation would probably need a whole different set of rules.)