Having to assume a non-zero possibility that anyone you interact with on HN is secretly Zuckerberg makes the whole experience just that extra little bit spicy, doesn't it
I think the connotations of "spicy" include danger, thrill seeking, and titillation. Whether that's "good" depends on your personal appetite for such things.
you could be excited by the (idea | risk) of Zuckerberg reading you writing bad things about Zuckerberg or Facebook, or saying these things to him without knowing. Like a game. This is how I understood the post and it matches your interpretation of spicy.