Infinite scroll, for example, makes it easy to lose your reading progress with a simple refresh/reload. Paged UIs, on the other hand, don’t have that problem.
Reddit is especially obnoxious because the sorting algorithms are extremely volatile, and if you do scroll too far, you'll never find that particular piece of content again.
Infinite scrolling in Twitter etc. is much less obnoxious.
I'm not even sure if it's 3PA only feature but there's option to hide all posts that you've read (or scrolled past). After finding that feature now i want it everywhere there's infinite scroll because yeah otherwise it's unusable.
That feature's way less useful when you don't read each and every post in sequential order. Also sometimes I want to go back and look at something I've already read. That makes it complicated too.
