I agree with all of those answers. Chidi is pretty hard to type, I am thinking ISFJ. He always relates things back to previous texts he has written and read, and is good at storing facts and information about random philosophies, which seems pretty Si to me. The Ne is there, but it doesn't seem strong and is rather weak even for an inferior function. He thinks of worst case scenarios and negative possibilities the future holds a lot and really lacks decisiveness. For enneagram, I am thinking 6w5.