Huh, really? I've embedded gifs here before from imgur.
Imgur doesn't treat all gifs the same way, and I'm honestly not sure as to why it does this, some are regular gifs, and then they've integrated a new format called Gifv that formats the gif simmilarly to, but not exactly like a webm but without sound iirc.
You can't download them like regular gifs either, you have to get directly to the gif, and then download it through the download button on the righthand bottom side.