This reverts commit c55429ac49.
Reasoning: The video has no height while the poster image is loading,
and then once it loads a moment later, it takes up extra space,
enlarges the video, and the page jumps. I don't know how to make the
page not jump while loading the poster. Width, height, and styles
look like they're set correctly.
Watched videos on your subscriptions feed will be darkened, and the
option to hide all of them has been added.
This only takes effect if you have enabled saving watched videos on the
server in the settings menu - default is off.
