I use two-finger trackpad scrolling on a MacBook, and since previews pop up at the cursor, and since my cursor is always near what I am reading, the popup always covers what I am reading and ignites a rageflare in my brain reminding me to disable javascript and reload the page*. It occurs to me that there would be no issue if popups positioned in either the farthest corner from the cursor (computed) or a non-obstructive region such as the left sidebar.
*I always dismissed the popups so quickly that I never noticed the gear icon, until today googling eventually informed me of it. However a slide switch like Youtube autoplay or some other binary control would have been discovered....