The concept is appealing, but implementation may be challenging and raises issues of its own. I guess particularly what does "socially" mean - in the context of my friends, my family, my community? regarding business interactions, sexual relationships or what kinds of interactions? Are there important categories other than those four that we should be thinking of? As well as more trivial issues such as how do we pronounce FFMF, or does each category only have three options (F, M, NB), and what sequence should they appear in.

I think that the bigger issue is that many of the arguments tap into much bigger issues. Two of which are: Who are the ultimate authorities on human behavior/appearance - what we learn from science or what is dictated by a religious authority.

Do individuals have autonomy over their bodies and identities or do they need to yield to the authority of others. (Clearly tied to #1)