[VydorScope]

Originally Posted by JohnGalt

I'm honestly not trying to be argumentative, but I'm very surprised by this assertion that the use of "they" singularly goes back centuries. Do you have any examples to substantiate that?

Actually it has been provided in this very thread more then once. Shakespeare was the big one mentioned already, but this one dates form the 1400's...

Historical usage: Geoffrey Chaucer is widely credited as the father of English literature. He was one of the first well-known authors to write in Middle English instead of the prevailing literary tongue, Latin, bringing legitimacy to the language. And, what’s this? Why, it’s a line from The Canterbury Tales, ca. 1400:

“And whoso fyndeth hym out of swich blame,
They wol come up [...]“

It’s a little hard to tell in the Middle English, but whoso is a quantified expression, like whoever, that is syntactically singular, but then is paired to the syntactically plural they. So, since at least the beginnings of literary Middle English, 600 years ago, it’s been all right to use singular they. It’s been consistently attested since then; Henry Churchyard reports examples from the Oxford English Dictionary in 1434, 1535, 1643, 1749, 1848, and a wide variety of years in between. There has literally been no point since 1400 when singular they went unattested in contemporary English.

It is also attested to by various grammars:

For example:

An English Grammar by Baskervill & Sewell, originally published in 1896, states that while he is preferred to singular they in general, they is “frequently found when the antecedent includes or implies both genders. The masculine does not really represent a feminine antecedent [...]” (Italics in original.) Further, as an exercise, they give examples of singular they, and tell the reader, “In the above sentences, unless both genders are implied, change the pronoun to agree with its antecedent.” (Again, italics in original.)

The simple fact is that they is grammatically acceptable to use a singular, and always has been.

And the current edition of the OED website attests to its usage:

You can use the plural pronouns ‘they’, ‘them’, ‘their’ etc., despite the fact that, technically, they are referring back to a singular noun:

If your child is thinking about a gap year, they can get good advice from this website.
A researcher has to be completely objective in their findings.

Some people object to the use of plural pronouns in this type of situation on the grounds that it’s ungrammatical. In fact, the use of plural pronouns to refer back to a singular subject isn’t new: it represents a revival of a practice dating from the 16th century. It’s increasingly common in current English and is now widely accepted both in speech and in writing.

So, yeah, its legit.