Didn’t work. Put something in the brackets.
(Crud, now it doesn’t appear as a link.)
What client are you using?
For me, it shows up as an embedded video (with video player controls) when using the default web UI and shows up as a looping image (without video player controls) when using Voyager. Both the version in my comment and the one in yours display the same, in both cases.
(Side note: I usually like to paste the image data into the comment rather than a URL to it so that a copy gets uploaded to the Lemmy server and doesn’t depend on third-party image hosts, but whenever I try that with an animated gif it becomes a still image. 🙁 )