> I believe this behavior has a lot to do with the mechanical act of clicking, the sound and feedback that for some reason feels good and ends up becoming a compulsion.

I'm a compulsive highlighter for most of the reasons people have described. I don't hear any sound when I click though, because I use a touchpad with no mouse buttons or clicking (tap to click, tap-tap-drag to highlight, two finger tap to right click, two finger scrolling).

Since I started reading a lot on a touch screen phone I've been frustrated by the lack of easy highlighting, and I compulsively scroll to track my place instead.