Animated webp test
Testing please ignore
Weird. The backend actually went out of its way to extract a static PNG thumbnail and uses that as the expando source image rather than using the post's webp image hotlink.
Conclusion: hotlinking animated webps does not yield an animated image as far as I can tell
I believe webm does work. Furthermore, it's been my experience that gif files are converted into webm upon upload.
webm
gif
Yeah, I thought the same, but I needed to prove a point in an internet argument