“It is the responsibility of all players to ensure the correct player is on the machine at all times.”
We have seen several threads where the interpretation of this text is varying widely. This text is causing more trouble than it is helping. It needs to specify actions required of the player or consequences or both.
I am not saying my interpretation is right, but I always read it as a reference to the previous sentence “Any points scored when a ball is being played out of turn count.” So my interpretation has always been, you have no ground to complain about the free points your opponent got. And that is all.
If it is more than that, it should be stated, such as, if you notice someone playing out of turn, “you should ask them to trap up and call an official.” Or “you are required at all times to stand right behind the player and watch like a hawk. If they are playing the wrong player you should run around screaming cheater at the top of your lungs.” Or “If you are having a smoke and someone plays the wrong ball you get a red card for not ensuring the correct player was at the machine.”