For example, I will order all mirrors removed from the palace, and scream and flinch whenever someone accidentally holds up a mirror, etc. In the climax, when the hero whips out a mirror and thrusts it at my face, my reaction will be “Hmm…I think I need a shave.”

Superman is obviously faking his vulnerability to kryptonite.  It’s highly suspicious that so many people have attempted to use kryptonite against him but none have managed to kill or maim him.  Also, doesn’t it seem implausible that someone would be fatally vulnerable to the radiation given off by his own planet?

Although some nay-sayers might argue that Superman is too honest to lie about this sort of thing, I think it’s just like a better version of his Clark Kent ruse.