what is unhumanity?
unhumanity mean that identify as human once in past, but not anymore.this means reject human standards, but may still want honour or emphasise human origin.

who would, and why?
- people with history in which others devalue and hate - they reject first, seem only fair take as compliment
- alterhumans/nonhumans who only identify later in life
- people who imprint on or adopt by nonhuman creatures/spirits
- people who want embrace what humans not understand
- ...and anyone who feel like fit meaning

this seem like bad idea!
unhuman do not mean hate humans.hate standards, yes. empathy, romance, worth, unspoken rules - not everyone meet these in same way. not everyone can meet at all.
can be kind without empathy and romance. can bring happiness without ever change world or produce anything "of worth". everyone deserve chance live.
these standards make that hard. people get sweep under and ignore when hurt, force to suffer in system that can not wait until able throw out.
as well, do you find that better appreciate things when not have? little bit like that.
can ache for summer sun in winter without.
can appreciate humanity at best when not force self to standards. when reject "belong."