Any modern browser visiting imgur gets H.264/WebM instead of the uncompressed gif. They introduced this 2.5 years ago. After a couple smaller gif only sites made the practice popular.
That is indeed what I meant by "efficiently recompressed." 10 seconds of H.264 video are still a lot larger than a JPEG.
of comparable resolution maybe, but the file size is still not large for say a 640x480 video, less than a few Megabytes.
I stopped clicking imgur gifv links a looong time ago. They worked for me maybe one out of eight times. By now I have an allergic reaction just to seeing them, even if the issues may have been fixed by now.
October 2014 -> May 2016 is 1.5 years, not 2.5. It's all of 2015 and bits of 2014 and 2016.