We recently programmed Bucket, the IRC chat bot in #xkcd, to allow people set their gender so he can use pronouns for them. This ended up taking hundreds of lines of code, three pages of documentation, and six different sets of pronouns and variables, just to cover all the basic ways people in the channel with different gender identifications wanted to be referred to (even without invented pronouns like “xe”, which we vetoed). And that’s just to cover the pronouns. The role of gender in society is the most complicated thing I’ve ever spent a lot of time learning about, and I’ve spent a lot of time learning about quantum mechanics.

— Randall Munroe (of xkcd) – Sex and Gender – (emphasis mine)

A Question of Gender Identity