Section 15 - Tournaments
22. Showing cards from a live hand during the action injures the rights of other players still competing in an event, who wish to see contestants eliminated. A player in a multihanded pot may not show any cards during a deal. Heads-up, a player may not show any cards unless the event has only two remaining players, or is winner-take-all. If a player deliberately shows a card, the player may be penalized (but his hand will not be ruled dead). Verbally stating one’s hand during the play may be penalized.
In a tournament, you can't expose a card (unless its heads up). Flipping over your cards subjects you to a penalty. Like Martini, the exposing player would not get any benefit from his action. It might be a case where he doesn't realize that he's making a ambiguous action. I'd explain to him why he can't expose his cards *before* he says fold.