It's a very fine line between what's allowed as non-fiction and what isn't.
For instance, if non-fiction is completely allowed, then people might see it as a way to post a "blog" here without needing to pay money or post 5000 times. That's not allowed because no story could come from that.
On the other hand, I know someone who posted a story about something that happened to her in school. She wrote it as a regular story, with dialogue and narration and everything like that. That was allowed because, well, there's a story in the thread.
So it's a case-by-case thing with non-fiction works. I don't want to ban them completely, but on the other hand, I don't want to allow them completely.
Did that help? :< I'm half-asleep, but I didn't want to leave you waiting for an answer.