Wolfster: I have searched RRoP, v11 and I cannot find anything that deals with cards exposed by a player, during a cash game, other than a very brief statement as follows from section 3, Irregularities, #12:
"12. Procedure for an exposed card varies with the poker form, and is given in the section for each game. A card that is flashed by a dealer is treated as an exposed card. A card that is flashed by a player will play. To obtain a ruling on whether a card was exposed and should be replaced, a player should announce that the card was flashed or exposed before looking at it. A downcard dealt off the table is an exposed card." I added the emphasis to the 3rd sentence.
In section 15, Tournaments, #22, RRoP says:
"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."
So, my answer to your question regarding cash games would be to check the 'House Rules'. If the topic is not addressed, perhaps it should be.
Hope this helps!!