Worth noting that this only works for Chrome. For what it's worth I don't support the practice and think it will not help prevent "self-XSS" at all. The idea of self-XSS being ridiculous to begin with.
Apparently it's common enough on Facebook, and not that ridiculous to imagine.
It's just like the "delete system32 to make your computer go faster" trick. For anyone on this site it's a laughably stupid prank, but you only know about it because there are people out there ignorant enough to fall for it.
Unfortunately, ridiculousness does not seem to prevent people from being hurt by it on Facebook.
What Netflix thinks they are defending against I don't know, though. Hopefully a Facebook user would think twice about some really long list of instructions of how to bypass the Facebook security. Since I can't imagine Netflix has the same problems with people being fooled into attacking themselves, they probably think this is some sort of security measure, but, that's a race they not only can't win, they can't even stay even with. Making it slightly more annoying to run JS? Sure. Making it impossible? Not gonna happen; the user has to much control over the JS context.
It's just like the "delete system32 to make your computer go faster" trick. For anyone on this site it's a laughably stupid prank, but you only know about it because there are people out there ignorant enough to fall for it.