Nit: please don’t push to my browser history every time I expand one of the sections… I had to press my browser’s back button a dozen or so times to get back out of your site.

You can also hold down the back button to get a menu of previous pages in order to skip multiple back button presses. (I still agree with your point and you might already know that. Maybe it helps someone.)

Thanks. I'll look into that. It was recommended exactly for backtracking but I get that if you want to leave it's a whole lot of backpaddling :-)