I'm still "seeing" them as a difference in kind and not degree (though I would classify that godaful Oz book as fanfiction. Even if it had been good).

I can't describe it. I just look at them and know they're different. You know how some people see different numbers as different colours, or taste different sounds? Or Karina sees a story as a wonky spiral that wobbles? It's sort of like that. Fanfic, to me, looks (or feels, or smells, or whatever sense reading comprehension uses) different than works sourced in something previous.

The problem, I think, is getting into semantics of "what is fanfiction anyway"?