I’ve long espoused the utility of the singular they as a handy pronoun for when the sex of the subject is hypothetical or unknown. But as a copyeditor, I’m beholden to convention—it’s not for me to tell an author they should use a form that some people consider ungrammatical. My job is to provide clarity and avoid bumps along the way.
The creator of the AP vs. Chicago website has turned her attention to ways in which words include or exclude, marginalize or empower. Karen Yin has created Conscious Style Guide as “an online resource for kind, compassionate, and inclusive language.”
The Associated Press Stylebook suggests treating none as a singular pronoun when referring to the absence of individual people or things: “None of us is perfect.” That’s a style choice consistent with what many consider good writing, but there is little to suggest that “none of us are perfect” is any less valid a construction.