I'm more interested in the metaphysics of the comment itself. It clearly exists in an ontological universe because it can be constructed but it cannot apply to itself because self-evaluation renders it false. So it is de facto meaningless but it is actually not meaningless because in the universe where "the only thing we know is that we don't know anything" we would now know two things. I guess that means we've learnt something?

Anyway there is some connection to AI and AGI in this that is worth exploring...