[quote=OtomostheCrazy]
Technically, Lore-wise, both Ornstein and Smough, along with their Souls and item Drops, were illusions created by Gwyndolin. You fight the Old Dragonslayer in Dark Souls 2, who has the exact same armor as Ornstein, albeit a darker shade, and drops the Old Leo Ring.If the one in Anor Londo is an illusion, then it would have made sense that he would be unparryable, since the Chosen Undead must be tested to see if he/she deserved the Lordvessel.
[/quote]
I'd forgotten about that theory. That means the Old Dragonslayer is in fact Ornstein (old-ass Ornstein), not just some look-alike. Yay for continuity :D
And i suppose that does justify the parry problem. Artorias' unparryability can be explained simply by his size (he's big even for a demihuman) aaand... that covers everyone, i think. Teh mystery has been cracked.