It's an imgur thing. It disables controls on every interaction with the video by doing `.controls = false` on the video element.
Chrome seems to ignore this attribute being set to false and continue to show controls anyway, which appears to be a spec violation from my reading of it. Of course it ends up being a desirable behavior in this case.
1) You go to https://i.imgur.com/vuUyLnz.gifv.
2) You decide to skip the beginning so you "Right Click > Show Controls" and use the controls to skip the beginning.
3) You decide to skip to the end so you move your mouse over to where the controls should be but they don't reappear.
4) They're gone and the only way to get them back is to "Right Click > Show Controls" again.
There are a lot of rough edges like that. I'd almost rather not use browsers than use Firefox in its current state.