Open an old library book and you will sometimes find, in the margin, a single word: “yes,” or “no,” or just a line under a sentence someone else thought worth keeping. It is a strange kind of correspondence — between a reader who has moved on and a reader who hasn’t arrived yet, mediated by a paragraph neither of them wrote.
annotation
a comment on a comment
Digital reading mostly abandoned this. Highlights get stored somewhere you never revisit. Comments live in a separate pane, disconnected from the sentence that provoked them. The margin, as a physical place beside the text, mostly disappeared.
What’s lost isn’t just the aesthetic of old books. It’s a particular kind of thought — the aside, the qualification, the “but consider” that doesn’t want to interrupt the sentence it’s responding to. A footnote defers the thought to the end of the page. A margin note keeps it right where it happened.
aside
proximity is the whole point
I think this is why marginalia has never really gone away, even in eras that don’t print. People still write in the gutters of PDFs. They still leave comments flush against the line they’re about to disagree with. The impulse to annotate in place rather than afterward survives the format.
A good margin note doesn’t try to be an essay. It’s closer to a raised eyebrow — brief, situational, and only legible next to the thing it’s reacting to. Move it and it stops making sense.
That’s the whole argument, really. Keep the comment next to the sentence. Let the reader see both at once.