Preview passage
Try selecting this text. The marks do not trap the cursor.
The best interfaces rarely announce themselves. They hold still long enough for people to trust them, then move with enough certainty that the next step feels obvious. A highlighter should do the same thing: sit on top of the words without swallowing them.
What matters is not just the color, but the way the ink starts, slows, and settles. The stroke needs a little unevenness so it feels drawn by a hand rather than stamped by a machine, and the text beneath it should stay readable, searchable, and easy to trust.
When two marks overlap, the darker region tells the same story a real marker would. That tiny detail changes the whole feel of the page, because it makes the layer feel physical instead of purely decorative. In practice, the thing people remember is usually the one they never had to think about: the smallest details are what make the whole surface feel alive.