Looks like the workaround for FiMFiction's "hidden chapter" problem doesn't
quite work under some circumstances. I tested it with
http://www.fimfiction.net/api/story.php?story=13070, which has four public chapters and one hidden chapter. Problem is that the hidden chapter is #4, with #5 being public. FFDL got all the text of the chapters correctly, but it used the name of the hidden chapter #4 as the title for the visible chapter #5. I've mentioned this specific case in a fresh PM to Knighty. Not sure if something this minor warrants further fixing in FFDL since it is after all just a workaround.
Oh, I found another oddball problem while using FFDL on FiMFiction.
http://www.fimfiction.net/story/49084/ gives the error "Invalid IPv6 URL". I've never seen that error before and there don't appear to be any weird URLs in the data the API gives. The story has only one image in it, in the first chapter, and I don't see anything weird about its URL either.