My guess is that they don't really want any interference with the rails at all, be it for safety reasons or the spirit of the game, and that trying to manipulate the ball with some arm or flail or whatever isn't allowed. Of course, that's something to go onto the Q&A.
Regardless, I think they are aiming more for making sure the rules are more like soccer than for any rules concerning the ball return here. Hope that helps.
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The board is a mirror of the mind of the players as the moments pass. When a master studies the record of a game he can tell at what point greed overtook the pupil, when he became tired, when he fell into stupidity, and when the maid came by with tea.
- Anonymous Go player