It also happened to me, but I wasn't using imgur as my image hosting site I used imgbb.com. Although, it didn't display any error like that of imgur but still yet the forum could render the image, so I had to delete the whole post because I was quoting an Op for visibility.
But the forum does not render images.
Honestly, I don't see much need in using .webp files, since a .png or .jpeg 90% has more than enough quality for most scenarios here on the forum.