The word "themself" seems wrong, and some spell checkers don't like it, e.g Microsoft Word always tries to correct it to "themselves", even in singular. It's in the dictionary though. Is it ok to use, or is "themselves" better, even for singular? E.g.
The body is just an external expression of who we are, but the soul is the person themself...
Which is correct? Why?
Note1: I am a fully native Brit, first language English, A in my English Lit and Lang GCSEs, but I just find this word very awkward and don't know why or what to do with it, so I am just here to ask for a full english lesson on the use of this word please.
Note2: this question is unrelated to the modern pronoun movement, I am just interested in this (much older) gender neutral pronoun.