I don't think English is the author's first language -- see the use of "defer" throughout the document. Maybe most polite not to nitpick.

I don't think it's meant as a nitpick but more of a "hey, you may not know this but here's a helpful thing". The comment seems to have been both worded and received in that positive way and that's a great thing if you ask me :)

Or use he or she instead. But yeah, they or he or she is most neutral.

Fair point! Thanks for looking out :)

I haven't heard of that as a best practice. In my English class in high school they only mentioned to keep it consistent. The preference should be given to the writer. Both men and women have contributed to society so their pronouns can safety be used in written text.

The problem is the male default. Grammatically it's fine, but when hundreds of article default to male, it has a growing effect socially. "They" or "he or she" is typically customary these days, more and more so the former as the latter is annoying to write and the singular they is becoming more accepted as a grammatical change in English.

we need a shorthand s/he :)?