"As the walker begins to move, she or he receives raindrops that would have fallen in front, while missing the drops that now fall behind. This creates a balance, and ultimately, the amount of rain received on horizontal surfaces remains unchanged, regardless of the walking speed."

This is wrong. The back, stationary or moving forward does not receive rain. When stationary, the top receives rain(ideal model). When moving forward, the front AND the top receive rain. I don't see the balance they are claiming.