- If someone feels that they’ve been unfairly passed over for a promotion, they should speak to their supervisor.
I'm afraid not.
As Mark Liberman writes, "singular they has routinely been used throughout the history of English, by all the best writers, until certain subcases were artificially turned into 'errors' by self-appointed experts. Successively less discriminating pseudo-authorities then generalized the proscription in successively sillier ways, although they have largely been ignored by the users of the language."
Similarly, Merriam Webster's online dictionary has this to say. "The use of they, their, them, and themselves as pronouns of indefinite gender and indefinite number is well established in speech and writing, even in literary and formal contexts."
Firsten still isn't buying it. He says that "strictly speaking" it's wrong. I take this to be based on the single-sense fallacy that often turns up in grammatical prescriptivism (see here). That is, a word has a single meaning and other meanings are wrong. In particular, because they means "two or more people or things that have already been mentioned or are already known about", it couldn't possibly also mean "a person or people of indefinite gender and number." This same argument would hold as ungrammatical it to refer to a person since it is "used to refer to a thing, animal, situation, idea etc that has already been mentioned or is already known about." Remember that every time you identify yourself on the phone.