I don't know if I deliberately developed a habit of highlighting the current paragraph when reading long articles, but it has become extremely useful.
In the same vein, I get easily distracted when reading text and the ability to click around, select and deselect text that I'm reading helps me to stay engaged.
Writing that out it sounds like it would be super distracting but its not (for me). Possibly related to the phenomenon where some people work better with noise in the background rather than in silence. Clicking around might help maintain a minimum level of stimulation while reading.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.