As an avid reader, I'm appalled for not knowing what a flyleaf is. I read that PBS allows autographs or inked dedications on the fly leaf and on the inside covers. I just received a particular book with a note to mom on the internal title page. Will I be able to repost it?

I think that is the blank page at the beginning of the book.  I would think you could post it as long as its not on the text pages.

I third the opinion.  Authors can (and do) sign any of the pre-text pages, or even inside the cover.  Based on the sum of postability guidelines (in addition to practical experience) TPTB don't get cranky over writing unless it's on a text page.  Unless the requester has a 'no writing' RC, it's doubtful you will have any difficulties posting the book (if it's otherwise postable).

http://www.squidoo.com/BookRepair#module9594969  This site lists the parts of a book.