I knew I was a highlighter but reading that showed me how much my brain relies on spam click highlighting to keep my eyes on track. I should probably read more books.
I do it one type of pointer or another for tracking my reading position continuously. I even highlighted some words in your comment while I read it. In a book, I typically put my finger (or the corner of my bookmark) under the 3 words or so I'm currently reading, or I'll put my thumb next to the line I'm currently reading. I don't usually think about it, but being on that web page and being prevented from highlighting made me back away quickly. If I'm not highlighting, then I'll also scroll so the top of the page marks where I am. (Whenever a page has a menu that changes relative position/size or pops up to cover the content when you change scrolling directions, that's an annoyance.) I think I use something to keep track of the current line like that more often than highlighting. Now that I think about it, if my mouse pointer were more noticeable, I assume I might simply point to where I am. Then again, the highlighted words are independent of the pointer, so it lets you have both.
Why? Maybe my eyes move away from the page while I think about what I'm reading. Otherwise you'd have to keep a visual lock on your reading position continuously right? Or you'd have to scan the text to figure out where you left off.
Technical term "pointer assisted reading" (which I don't think includes the repetitive ADHD behaviours).
My google-fu failed to find a good article about it.
Appently the behaviours are best described within the comments of nerdy sites that have more mouse-users.
Edit: obsessive "highlighters" please: what do you do on your mobile devices? What do you do when using a keyboard without a mouse? Do you do it with trackball devices or laptop trackpads?