How much metadata?
That’s a series of screensnaps from the ePub editor, SIGIL. Those designations are just for Author.
A example of possible user-contributed metadata linking:
I once had a wise and honest teacher; I asked him one day to explain a certain matter; and he replied: “I haven’t time now. If I knew it thoroughly I could tell you in a few minutes, but as I know it only imperfectly, it would take me an hour.”
— Footnotes to Life by Dr. Frank Crane, published 1920
connects/relates loosely to:
I have made this [letter] longer, because I have not had the time to make it shorter. –Blaise Pascal
— quoted in The Art of the Start by Guy Kawasaki, published 2004