One question: For 1E: It takes two, can other author be illustrator? Or they have to be the "author"?
Good question! I don't think we were looking at the square from that perspective. Probably something for @JaymesRS@literature.cafe to weigh in on, honestly. Personally, I don't think stretching the square to include illustrators is a problem, especially if the illustrations add to the experience significantly and/or in collaboration with the text. Graphic novels and picture books would be the obvious yeses from that perspective, but whatever you think qualifies would also be good with me.
Still reading There Is No Antimemetics Division by qntm. It's taken quite the cosmic/eldritch horror turn in the second half, which is great.