Take this comment as an example: https://lemmy.dbzer0.com/comment/20455448

There are a few images with notable resolution (500×500) in that vote comment, that are shown at very small size. Whenever they come into view, the fps of the entire app drops notably for me, down to perhaps the tens. I've seen it go even lower on other votes with more emoji.

My phone is quite powerful, and browsers for example can display similar cases fluently even on much worse hardware.