Nitpicking (Preventing brute force ssh attacks)

Yes.  I'm not sure what your point is, though -- I already agreed that adding port knocking is
like making your password longer, and there's nothing magical about a 64K alphabet.  It just
means that a single knock gives you about 16 bits of entropy, as compared to 6 bits from a
random ascii character, so 1 knock gives a bit less than 3 (good) password characters.  Or...
you can just use a 4096-bit key and be done with it.