(1) I believe that all your sentences are great.
(2) Many of my favorite books are marked up -- in ink! I have
learned the hard way to mark them up only in pencil.
Then I can erase certain notes that later prove incorrect.
(3) I read somewhere that if one doesn't mark up a book (or even
s/he is not really reading it!!!
(4) As they say: context is everything. For example, I believe that
"mark up" would have a different meaning in:
That bookstore has lost a lot of business because it recently
marked up all books by 25%. = raised the prices. They had better
mark down all their books!!!
***** NOT A TEACHER *****