Heidi Brayman Hackel’s study of that period’s book use among “less extraordinary readers” - and that would be everyday folks, like us - suggests people added various types of marks while reading their books.
Here I can't help but wonder about people who wrote their notes or annotations into their own personal commonplace books rather than directly in the texts themselves. Perhaps somewhat tangential to the broader ideas here, but do the annotations necessarily need to be in the text themselves? What sorts of separate lives do unlinked annotations go on to have? What do annotations over the ages have from living within the text itself, separately in notebooks, notecards, commonplace books, or even in the modern age with digital annotating tools that can be seen, read, and distributed to much larger audiences?