They is, and has been for a very long time, perfectly valid for singular use.

Most people I've encounted do it all the time without noticing between sentences.

Where you you see a gender qualifier in the post? If you don’t know you don’t assume because you turn into a donkey or something like that.

what? where? look at the username, that's clearly anonymous, the hacker group.

In english, they stands for both plural and gender-neural (when you don't know whether the person you're referring to is male or female).

They has been used to refer to an unspecified individual since before you were born.

There's not a man I meet but doth salute me

As if I were their well-acquainted friend

A comedy of errors, act IV, scene 3