When I'm reading Hacker News my eyes are on the comments, the mouse pointer is on the left or right side so it isn't causing any distraction. I do it all the time. Sometimes I also highlight what I'm reading, mainly if I'm multitasking and it's a long text, I want to know where I started last time I lost focus on the text.

Re: highlighting, I do the exact same thing. Has always made me wonder about an add-on or something that could handle that in a way that gave it advantages over the highlighting method?

Then again, highlighting is low-tech, easy enough and works fine. Maybe I'm looking for an idea that isn't there.