The special "Author's Note" block is apparently something that was added during the big site revamp, so they're still pretty rare. I'm sure I remember seeing some at the tops of stories before but I've not yet found any examples trolling back through my recent reads. I'll keep an eye out.
This chapter had another at the bottom
, this chapter was nothing but an image and an author's note,
the updated FFDL handled them all okay. I also tried a couple of stories without author comments and those worked okay too.
I see that the various div containers have nice unique class names, so should it be necessary I can even do some nice automatic reformatting in the future. Thanks! This is exactly what I was hoping for.