When we’re working, we keep our dictionaries close at hand when we edit, and we do this for several reasons.
First, our clients’ preferences determine what our go-to reference will be and which resource gets the final say in case of disagreement. In some cases, the authors’ preferences—especially in the case of nontraditional spellings or made-up words—can trump all other resources. (It doesn’t matter if the author spelled XXXXXX like that, even though the dictionary prefers XXXXX, especially when it’s a sequel to a previously published work!)
Second, and we’re not ashamed to admit it, we don’t know every single word in the English language, and in some cases, some terms are very specific to certain industries or fields where we don’t have the same expertise-level knowledge as the author. (If we had doctorates in biology, physics, astrophysics, economics, American history, world history, chemistry, medicine, law, and philosophy, we probably wouldn’t have time for editing.)
When we read and edit, we try to pay attention to an author’s intent and try to assist him or her in selecting the most appropriate words. Notice that when we say most appropriate, we don’t always mean correct; this is especially true of fiction. In nonfiction, using an incorrect or inappropriate word can call an author’s credibility into question. If fiction, however, the incorrect word can be used as characterization. What does it say about a character who consistently uses the wrong word? What if a character uses the same fifty-cent word repeatedly, whenever he’s given the chance? What if a character uses an outdated term or one now considered offensive?
Word choice can be powerful when applied correctly, even when the word is used incorrectly.