Back when I wrote software documentation for companies who produced software, we had a style guide and prior versions of manuals to guide us. If a reviewer or reader asked us to write in passive voice or use "they" as a singular pronoun, we had the guide and the canon of existing documentation to back us up.
This morning I'm working on some feedback from a subject matter expert and I'm seeing a lot of suggestions that are stylistic that I'm loathe to accept ("they" as a singular pronoun is one). I'm torn between "He who pays the piper calls the tune" and "You're paying me partially for my expertise, and my expertise says that some of the changes you request aren't in the best interest of the reader." And yes, part of me is also thinking, "How can I ever include this in my portfolio if I make some of these changes?" (There are other suggested changes besides passive voice and improper pronouns that would make it look like I don't know what I'm doing.)
For those who have worked in places without a style guide, editorial function, or other professional writers, how have you handled it?