I remember the first time I absentmindedly pressed . or , on YouTube and was shocked that they used MPlayer's keybindings (and implemented such an obscure, but useful, feature). Oddly probably the least copied feature across video platforms, I like it a lot, but nobody else seems to have stolen it. (Can anyone believe that Twitch has gotten away with such a terrible player? I remember people used to send streamers Twitch VODs to review, and every time they paused the video gets greyed out. Twitch never changed this, and now people use YouTube for that.)
