[barmar]

 FrancesHinden, on 2013-August-31, 10:43, said:

The actual basis for South's claim for an adjustment seems to be nothing about the MI, but that he assumed 4S was a cue bid and didn't ask, and then found it had ended the auction.

If you held that South hand, and heard the explanation that 4♦ was strong and natural, would you ever imagine that 4♠ would be passed?

Asking about the 4♠ bid is a good way to get your side into UI trouble, as it suggests you have something in spades. So it seems like he's caught between a rock and a hard place.

[FrancesHinden]

 barmar, on 2013-August-31, 21:14, said:

If you held that South hand, and heard the explanation that 4♦ was strong and natural, would you ever imagine that 4♠ would be passed?

Asking about the 4♠ bid is a good way to get your side into UI trouble, as it suggests you have something in spades. So it seems like he's caught between a rock and a hard place.

Yes I would. I have a rule in all auctions like this (although I no longer play 4D as natural) that new suits are natural and non-forcing.
Don't forget that LHO, who thought that 4D was strong and natural, passed 4S. So he certainly 'imagined' it.

I still don't understand how South was damaged by the MI about the 4D bid.

4D non-leaping Michaels is not necessarily weaker than 4D strong and natural. It's also commonly played as forcing (although obviously one could ask about this). So I also don't understand why South would double a forcing bid for penalties but is passing a non-forcing bid.

[barmar]

 FrancesHinden, on 2013-September-01, 03:25, said:

Yes I would. I have a rule in all auctions like this (although I no longer play 4D as natural) that new suits are natural and non-forcing.
Don't forget that LHO, who thought that 4D was strong and natural, passed 4S. So he certainly 'imagined' it.

I'll bet if he could have seen the 5 spades in your hand, he would have imagined differently. While freaky distributions like this are not unheard of, they're not that common, and this tends to affect your (or at least my) expectations about suspect bids.

If RHO opens 1♠ and I have 5 of them, I'll believe it's a freaky distribution (although a psyche wouldn't surprise me). But if a strange spade bid comes up later in the auction, I'll be inclined to expect it's artificial.