Go read the thread.
The sword's a plot sheild. Nintendo's all but stated it directly, and the only reason they won't is the same reason they waited until Twilight Princess was announced to declare seperate Links, because they like to leave us in the dark and maintain creative leeway.
The fact is, the sword clearly stops such crap, and if Link took, say a light arrow, and threw the head of that, he wouldn't have to worry about regen anyway.
Edit: .. That's not my Mariofacepalm.. =[ DAMN YOU, CC