Earlier quoted context omitted.
Umber Eco was one of the greatest scholars of Middle Age's philosophy. It is a great delight for all of us that he decided to share his knowledge in the form of a Novel. I don't think you can find any other writer capable of translating the thinking of ordinary men from Middle Ages into a book like he did.
It's not medieval philosophy, with "years after that conversation was set", the poster you're replying to means 600 years. The book should not be seen as an historic work.
I agree that the Name of the Rose is not an historic work (incidentally so did Eco), but plenty of medievalists think that it is good enough to be a useful teaching tool:
http://www.syracuseuniversitypress.syr.edu/fall-2009/postscr...