The person you are referring to doesn't need to be trans for you to use "they" instead of "he/she". You can use it as a direct replacement of "he/she" in every instance.

That's new. As I was taught, "they" usually refers to more than one person.

@Allure Dan Fox (academia.stackexchange.com/questions/119396/…) made a similar remark

The authors should probably not know the referee's gender in a blind review process.

If you have to use pronouns in situations where you don't know the author's gender, -- In my experience, it is quite trivial to avoid using pronouns altogether, when writing a review response (for example by referring to the reviewer as the reviewer, similarly to using the OP on SE)

@Allure, the singular 'they' has been around since 1375 (public.oed.com/blog/a-brief-history-of-singular-they)

@Allure "They" is often used for a singular. Example: "The suspect appears to have smashed the lock, at which point they entered the household."

@user53923 - Spot on. It's hard to know for sure without seeing the entire sentence, but, in this case, instead of writing, "the reviewer and his concerns," the author could have perhaps used, "the reviewer's concerns."

@LamarLatrell Crucifixion has been around since 3rd century BC, doesn't make it right though. ;) (ncbi.nlm.nih.gov/pubmed/14750495). Yes, a little bit of joking there, but my point is just because something has been done for a long time doesn't make it right, or mean that it should continue to be done. :)

While the singular-"they" has a long history, it's my understanding that folks in the 1900's tended to object to it. xkcd did a strip in 2006 reflecting how it was something people talked about back then. Today the singular "they" can be used in all cases in which there's no need to specify gender, even if the gender is known. Conceptually, I'd liken it to the debate about retaining subtype information when an interface or parent type is sufficiently descriptive.

@LamarLatrell But is it recognized by any widely used style guides? And if so, was that a change within the past few years?

@LamarLatrell It is true that "they" has a long history of usage when referring to someone who's identity is somewhat generic; ie. as a near synonym to "one". But prior to about 30 years ago it was never used to refer to a singular person of specific (even if unknown) identity. See here. Some people may not like the author's usage of "he" for political reasons, but it is not incorrect, and very unlikely to be any form of aggression. It is just standard English.

Good discussion points. I should point out that my comment was triggered by Allure's assertion that it was 'new'. In reading her statement again, I see that it is possible, if not likely, that she meant it was new to her specifically.

The use of "PS: I'm female" may be confusing without context here. The editor may not understand the problem, and could just be wondering why you're telling them that fact about yourself. I get the desire to make it short, but it may be necessary to explicitly link it to the choice of pronouns in the response to be understood.

@LamarLatrell I meant "That's new to me".

@ZachLipton that postscript would be appended to the review, so it should be clear who it's addressed to.

"PS: I'm female" sounds like a terrible idea. First, it may be misinterpreted by the editor or the authors (or is that even remotely clear, if one was oblivious to the use of pronouns?). Second, in many fields where women are underrepresented, it's a potential immediate breach of anonymity...

@jmpc26: Not a style guide in the same sense as the Chicago manual, etc., but Steven Pinker's The Sense of Style clearly endorses singular they as acceptable English.

@user53923 What gemder-indefinite abbreviation/acronym would you have used? Replaced every he with "The reviewer"? Seems rather verbose.

@Basic Indeed. It is somewhat more verbose, but in my experience the word does not occur that often in the end. I can see that depending on your writing style (or the particular reviews?), it could be an issue