> I frequently hit Fn instead of Ctrl and don't realize what's happening until I look at my keyboard. And that's not when I'm in distress. Same goes for middle click. It's not a consistent interaction.

Triple Shift that you can only on a single website is worse since you're even less likely to be able to use it in distress

Besides, as a site you can try to add typo-similar combinations for your "hide" action (like alt+w or win+w) instead of creating a totally different one