Its all the rage at major Universities today. That and crying booths that provide a safe place for a good cry before a test on what gender correct words are no nos today.
The car is rented too, and last time they charged me double to cover the cleaning fee in order to get the smell out. I'll take you out to the woods, if you're into that type of thing . . . wait, Carbie! Come back, Carbie! Why are you running away? Where are you going?
It's not incorrect when referring to an adult male human.
I think Personhatten would sound a bit weird.
The name Manhattan comes from "Manna-hata", as written in the 1609 logbook of Robert Juet, an officer on Henry Hudson's yacht Halve Maen (Half Moon). It is theorized that the word might derive the Lenape tribal word Mannahatta, possible meaning "island of many hills." In English, the variations of a word follows the norms for the language of its origin, so "Manhatten" could never be incorrect,
unless somebody one day discovers that it means something quite different and inappropriate in Lenape. ;)