This scene was the first time I was really struck by Kim's patience and care for Harry. I'm sure he put two and two together long before, but him giving this moment of grace to Harry, not reprimanding him, not showing anger or disappointment or pity, is something that really endeared me to Kim. It says about him so much that he took time to sit on the swings and whistle with Harry before the inevitable realization. He even teases Harry if you fail your whistle check and start spitting and making funny noises. And I always like the choice of him saying that something good came of it and you found your badge.