Especially, moreover, must we restrain impudent youths from handling books—those youths who, when they have learned to draw the shapes of letters, soon begin, if opportunity be granted them, to be uncouth scribblers on the best volumes and, where they see some larger margin about the text, make a show with monstrous letters: and if any other triviality whatsoever occurs to their imagination, their unchastened pen hastens at once to draw it out.And now those trivialities are priceless marginalia. Who knows what men 700 years hence will make of today's cursive jottings and highlighter illuminations? Incidentally, the most amusing undergraduate annotations I've seen were in a collection of Samuel Johnson's observations on Shakespeare. Two consecutive passages scorning the Bard's penchant for wordplay were each marked by some freshman hand with a defensive "Wrong!"; and after the third, the defiant pronouncement, "Fuck you Mr. J". And they say Shakespeare isn't still relevant!
— Richard de Bury, Philobiblon (1345).