I love to complain about infinite scrolling, but this... is actually pretty clever. I'm not a huge fan of the everything-in-a-modal approach or URL manipulation (i.e. Discourse, which involves a lot of scroll listening and only gives you an approximation of your scroll position), so I think this is a good alternative.

Now for something a bit more ranty, in keeping with tradition: why the heck does the infinite scrolling interface at https://artsy.net/browse/artworks have a footer?