You have to be careful about which types of content you remove, though, to avoid breaking the browser’s Find. (Reddit is an example of a site that currently does this wrong.)
I spent a lot of time on Reddit and have never seen infinite scroll on it except when I had the 3rd party plugin "Reddit Enhancement Suite" installed. Is it in the new layout they pushed out recently, or do you have RES installed?
If you inspect you will notice that previous invisible items are represented by a single large div who's height increases as more items are scrolled out of view.