One of the hardest decisions editors make deals with consistency. To be credible, authors need to be consistent. They can’t say something is black one day and white the next and expect people to believe them–unless something is both black and white and alternates between the two daily.
Yet, people are often inconsistent and go with what works at the moment. Editors use manuals as the standard for their work, but sometimes there are reasons to deviate. For example, Chicago Manual of Style says to rewrite sentences to avoid pronoun/antecedent disagreement. That means if what the pronoun refers to (antecedent) is singular, the pronoun is singular. However, in our politically correct society, we’ve evolved to using the plural (they/their) instead of the singular (he/she, his/her). That’s not okay with Chicago and the manual says the author should rewrite the sentence.
While I’m pretty much a stickler for following Chicago when I edit books, I am inconsistent in allowing this standard to be compromised. I allow a plural pronoun (they/their) with a singular antecedent when we don’t know the gender (any student or anyone). Why? It’s easier for reading flow than he/she or his/her.
Another rule editors follow is change passive voice to active. Anyone involved in writing has heard of (or maybe even used) Strunk and White’s book, The Elements of Style. While the active voice is more forceful, it isn’t always the better choice. Sometimes it’s okay to use passive voice. For example, use it when there’s no ownership assigned to the action (It was reported that you came in late three times this week).
Finally, editors don’t need constant consistency in placing headings and subheadings whenever a new concept is introduced in a nonfiction book. I’ve seen books with headings every three or four paragraphs, as the author introduced a new concept in a chapter. While this is effective after a list of bullet points because it helps the reader find the text connected to the bullet points, it is not usually effective in straight text.
Yes, strive for consistency for your reader’s sake, but be aware that constant consistency can detract from your message as well. Have a reason for the deviation, that’s all.