How about the most depraved volume control design of all: the actual reddit web video player (at least the embedded player on old.reddit)?

The slider is hidden by default. Hovering the volume icon makes the slider appear. There is margin between the icon and slider, though, so you have to quickly "zip" your mouse across this gap/chasm before the slider disappears. If you make it over to the slider in time, your hover then preserves its visibility.

I know for sure the devs at Condé ain't dogfoodin' on that interface anymore!