Okay, so APPARENTLY a singular, gender-neutral "they" has a long and proud history.
APPARENTLY, even Willy T. Shakespeare used "they" this way!
And APPARENTLY, I'm not unarguably in the right when I say that "they" is always plural. FINE. Everyone makes mistakes; I suppose it's fair that I'd FINALLY get my very first turn at bat. But that doesn't mean English is getting off scot free! We still need an UNCONTENTIOUS gender-neutral pronoun.
What happened to "thon"?
In a shouted sentence?
THON NOT KNOW WHY NOBODY LIKE THON
There are still some other alternatives you haven't considered, T-Rex!
Such as?
How about "yo? As in, "Yo doesn't know what yo thinks about this." Or "bitches", as in "Bitches didn't derive that function properly". Men can be bitches!
Man. Men CAN be bitches.
Bitches don't even know.
Later:
Bitches is now singular, tell bitches.