A bit more info to add based on observations made the past few minutes while navigating the site. The ad expands when my cursor passes directly over it (which is to be expected, but is a bit annoying given the location of the ad, since scrolling up and down the page with a Mac touchpad often leads one to unwittingly expand the ad). However, it also expands when my cursor passes over any location where the ad is designed to expand when triggered. In other words, the ad will expand whenever my cursor passes over the portion of the thread where you see the ad in the second pic I posted above. If I keep my cursor all the way to the right of the screen, I can avoid the problem.