I got comments on this one report I wrote today and he underlined every time I used the singular 'they' and seemed confused that I didn't actually mean there were several people.
Modern English def still uses singular they even in a scholar context, there's just a loud contingent of prescriptivists who insist it's Wrong but honestly prescriptivists will insist a lot of things are wrong
YEAH I was thinking if he's ESL and had no reason to look up singular they usage, he might've just been thrown be the vocal pushback to it as being correct
doesn't help with your personal usage tho