Georg: The example is actually a violation of rule #41 - No Disclosure. That rule says, "Players are obligated to protect the other players in the tournament at all times. Therefore, players, whether in the hand or not (emphasis added), may not:
1. Disclose contents of live or folded hands,
2. Advise or criticize play at any time,
3. Read a hand that hasn't been tabled.
The one-player-to-a-hand rule will be enforced.
I understand this is difficult, but it is a matter of educating your players (which may take some time, as bad habits are hard to break) and the only way to do that, in my opinion, is to make sure they know the rule, the reason for the rule and that it will be enforced. As said in another question, the decision of whether to apply a warning or a penalty (or for that matter, what level of penalty) is up to you as the TD.
Hope this helps.