I wasn't 100% sure this was a problem, as I had noticed a lot more people commenting what appeared to be static image responses to comments. But there's this thread: https://lemmy.world/post/16932878 which makes it easy to be sure that in fact they are definitely GIFs, and they don't play when you click on them. It just opens the first frame of the GIF like a static image.
There is currently a bug with our image viewer that it seems to use imageloader that is set on the application level (which is controlled by that setting) instead of the one that is passed into it(which has it always enabled).
Well that's weird. I turned on that setting, reloaded the app, and now they don't exactly "play", but their frames kinda change randomly when I open the GIF in the image viewer and tap the screen to toggle between full screen and having the back button visible. Almost like it's "playing" in the background, but only getting redrawn when something else makes the view update.