.....Themself is arguably not an English word, and most certainly
not in common usage.
'Themself' exists, it's English, and I can't think of any definition by which it's anything other than a word. However, as you allude to, it is limited to informal registers and much less common than 'themselves', even with a singular reference, as your example illustrates
"will the person who reserved the Oxford English Dictionary please make themselves known to the head librarian"
In fact, it is so rare and informal that written examples are not that easy to come by, though a quick trawl through google throws up a few, eg. '
10 Internal Arguments That Every Londoner Has Had With Themself'.
The bottom line is we need gender neutral singular pronouns. I guess we'll keep trying different ones until something sticks. It may indeed include "themself"
No need. English has coped quite happily for centuries with unknown gender, and indeed any reference to an unknown or indefinite person, through use of singular they. The difficulty that some people have with accepting this (and I'm not aiming that at you) constantly baffles me.
