Some tentative thoughts on the principles involved, having recently given a couple of "simple rulings" about which the players concerned are still doing vast amounts of ear-bashing.
The relevant passages from the Laws are:
Quote
73D. Variations in Tempo or Manner
1. It is desirable, though not always required, for players to maintain steady tempo and unvarying manner. However, players should be particularly careful when variations may work to the benefit of their side. Otherwise, unintentionally to vary the tempo or manner in which a call or play is made is not in itself an infraction. Inferences from such variation may appropriately be drawn only by an opponent, and at his own risk.
2. A player may not attempt to mislead an opponent by means of remark or gesture, by the haste or hesitancy of a call or play (as in hesitating before playing a singleton), the manner in which a call or play is made or by any purposeful deviation from correct procedure.
73F. Violation of Proprieties
When a violation of the Proprieties described in this law results in damage to an innocent opponent, if the Director determines that an innocent player has drawn a false inference from a remark, manner, tempo, or the like, of an opponent who has no demonstrable bridge reason for the action, and who could have known, at the time of the action, that the action could work to his benefit, the Director shall award an adjusted score (see Law 12C).
Now, the important words in Law 73F are the first clause:
When a violation of the Proprieties described in this law results in damage to an innocent opponent... These are often ignored by those who believe that just because a player who appeared to think had no apparent reason for thinking, that
in itself is sufficient reason to adjust. For redress to be due, there must have been a violation of Law (or Propriety, which is the same thing nowadays), and thinking is not a violation of Law. If this South thought he had something to think about, then whether or not (in the opinion of better players) he should have been thinking about it at all, he has not violated 73D2 - that is, he has not "attempted to mislead" by pretending to think.
Nevertheless, he has (or may have) violated 73D1 by not being "particularly careful" when his variation in tempo might work to the benefit of his side (as it appears to have done in this case). That is the reason it is still appropriate to use Law 73F in favour of East-West - as Jeremy correctly remarks, thinking on tram tickets after 1NT-pass-pass is an old dodge of which no self-respecting player nowadays should even be suspected.
But it is not always the case that Law 73F can be used when there has been no attempt to mislead and no dereliction of the duty of "particular care". I summarize the two "ear-bashing" cases briefly below, in order to exemplify my way of thinking with an acknowledgement that I might have been wrong in either case or both.
Case 1: a player was defending 6NT after a relay auction in which declarer had shown a 5=3=3=2 shape. At a critical point, he asked dummy to confirm that declarer really had shown 5=3=3=2. "Yes", said dummy. Dissatisfied still, the defender asked declarer to confirm that he really had shown 5=3=3=2. "Yes", said declarer, and added jocularly something to the effect that "...but you know what these systems are". Concluding from this that declarer was instead 4=4=3=2, the defender discarded the wrong thing and let the slam make because declarer really was (gasp) 5=3=3=2.
My opinion was that although declarer's remark was (to say the least) inappropriate, it was not an attempt to mislead, nor did it fall foul of the need to take "particular care". There was no demonstrable bridge reason for making the remark, though, so had it not been for the opening words of Law 73F I would have adjusted the score anyway. But those words are there, and they are there for a reason.
Case 2: declarer in two diamonds doubled had a trump suit of K7432 facing 1065. He led an early round from his hand - two, jack, five, eight. Later he led the six from dummy and caught a very slow nine to his right. He thought about it for a long while, then lost the king to the (now singleton) ace on his left and was down one instead of making.
The bidding had marked RHO with next to nothing, and there was no doubt that had the
♦9 been played in anything like normal tempo, declarer would have ducked - he almost ducked anyway, because he knows about the "own risk" provision of Law 73D1. But there was also no doubt that the chap who played the nine slowly was just wool-gathering - there was absolutely no "attempt to mislead", and no violation of Law 73D2. (You may say that this implies a trust in the chap's character that might not be warranted, but you will have to take my word for it that the chap is as honest as they come). Here, though, there
was a violation of Law 73D1 - the chap had failed to be "particularly careful" when he should have been.
These are deep waters, and as has been made clear by the replies so far, nothing very much actually belongs in "Simple Rulings" at all.