Well, I was really thinking what I typed. Someone down = one free hit on him. In every duel (on the duel server) I did and knocked someone down, I had to stop the next swing to prevent myself from attacking the opponent when he's on the ground. In a group melee, however, it's possible to avoid that hit, when a good player tries to save you and hits the enemy first. So I don't really see the point of this suggestion.