Why exactly do people underline large passages of _library_ books? Why, in particular, did one of the two people to previously borrow the book I’m currently working on underline large (and often random-seeming) passages _in pen_? It can’t be that much use for going back to. A notebook telling you which are the key pages/passages would do that, and the text that you’re meant to highlight is harder to read once it has pen lines all over it. If you really want to (a) remember a passage and (b) record it in a way that you can go back to, the answer is to type out the passages into a Word document. So this practice seems imprudent as well as inconsiderate.</rant>