While the artist is definitely messing with people, and that is the closest thing we have to a name (and is therefore the best thing to tag), "They" is just weird as a name.
In different commentaries made by the artist on twitter they're calling the character just "human". For danboorus purpose it's always better to have any kind of character tag for characters. You just have to look at all those *-haired-girl tags. So, the character can either be called "they", which is at least used on one image or *-haired-human or something else with *-human. Given that the artist calls that character mostly just "human" also means, that he doesn't want to decide if it's a boy or girl.
