We've all heard about keeping story continuity, so I won't be talking about that. Perhaps a better title would have been tightness...I digress.
Inigo inherited his father's sword.
He used his father's sword to do it.
He left matching scars on the Count's cheeks (not to mention giving him all the same wounds he received in the course of the battle.).
That phrase (see above, as I don't feel like retyping it.) drives the Count mad during the battle and empowers Inigo.
And that's a small portion.
It all seems to be so very tiny, a thing here or there, but isn't that what separates good from great? Great from classic? Classic from Don Quixote?