I'm here to talk about pronouns. Not to criticize the growing tendency to use "they" to refer, not just to single hypothetical persons of any gender, but to specific known persons who prefer not to use gendered pronouns. What I'm here to do is to caution writers on its use.
I hope that most people who care about their writing have noted already the extreme care one needs to exercise with pronouns when writing about a complex interaction between two people of the same gender. You need to be very careful that, whenever you write "she", or "he" as the case may be, it's clear which of the two people the reference goes back to. If it's unclear, your writing may be very confusing or even positively misleading. I see problems in this area occurring all the time. In practice, this is one of those things that writers usually can't see unless they put their work down and come back to it later, which sometimes there isn't time to do, or unless the work will be reviewed by a good editor, a rare commodity.
It's striking how much easier it is to write about such an interaction when the two people are of different genders. Then you can just drop in the words "she" or "he" without a second thought, confident that they'll always go back to the same person regardless of what else has intervened since the last name reference. When I was writing fiction, and consequently who interacted with whom was a matter of my unfettered choice, I would usually make one-on-one conversations between two people of different sexes, because I'd noticed how much easier those are to write. And this was over forty years ago, because I haven't written any fiction since then.
Well, "they" has even more writing traps. Not only can it be unclear which of two persons "they" refers to, but it can also refer to both persons, or even to something that's not a person at all. And that means writers have to be even more careful to avoid ambiguities.
I just came across a curious example of this. It was in an article by Matt Ford about the current state of the impeachment inquiry. Ford writes, "The original whistleblower's central claims are so thoroughly corroborated at this point that their testimony almost seems unnecessary." The possessive pronoun "their" surely refers to the whistleblower, whose sex or gender is unknown. But the topic of the sentence is not the whistleblower, but the whistleblower's claims. Which would also be referred to as "they" or "their". Could the claims give testimony? No, I guess, but they could be given in testimony.
This isn't really ambiguous, and even if it is ambiguous it isn't treacherously misleading, since there's no ambiguity of person. But it's awkward. It trips the reader up momentarily, like a loose or ill-fitting cobblestone in the pavement. And if you're trying to write a straightforward news article, and are not playing around with experimental prose, why would you want to trip the reader up? There's obvious reasons not to use the assumed "he", but it would have had the advantage of whipping the reader past the claims as sentence topic and focus it on the person.
Since we don't do that any more, we have to be more careful in our writing. So watch it. Be cautious with your "they"s and "their"s.