MFA

As a general philosophy I would tend to assume they made a mistake and use all the information even that I'm not entitled to in the first place. Also against strong opponents. Each situation has to be analyzed individually of course. But defending is hard, and visualizing declarer's full count problems is even harder. Defenders tend to worry mostly about not costing tricks objectively. I think I'm a little more sceptical when it comes to someone unnecessarily displaying high cards that could potentially make me play the other defender for some specific card. But still my starting point is that they probably just made a mistake.

Perhaps: 2NT - 3♦ (short hearts) 3♠ - 3NT 4♥ - 6♣

Pass. Too risky and pointless to bid. I don't see bidding for the lead. We are on lead against hearts ourselves, so it's only relevant when LHO misfits hearts, and then bidding seems particularly dangerous.

I would bid/lead like Codo and JLOGIC. (On these 5 hands, that is...)

Wtf? Nobody west of the pond bids anything. Instead everybody goes around marveling at meckwell bidding european style, lol (general remark unrelated to this problem). ;)

2♦, but just barely.

Even 5431 usually bids 1♠.

Who cares what is common in the US? :) I prefer very wide range 1-level overcalls with NF responses and transfers starting with opener's suit. Overcaller doesn't go out of his way to pass an advance though, but he can have a quite ridiculous hand. At the 2-level it's a different league. Then we start to care about suit quality and we usually have 6 cards. New suits are forcing now. I don't subscribe to the theory of overcalling 2♣ over 1♦ with rubbish, just that it could be marginally looser than usual. 2♥ over 1♠ could be a bad suit. If third hand neg. dobl. then advancer can't "escape" in a new suit. If he bids something he has a hand.

If we are not sure that the double shows ♣J as well as ♣K, then we should just leave out that card and count one space for ♣K only.

When he doubles the cuebid we can assume it shows ♣KJ. Those two cards we can count in. But I agree not the small ones we see during the discards. In other words, before the play starts, LHO will be 13:11 favourite to hold any other specific card. So knowing about ♣KJ is significant for vacant spaces calculations.

The answer, as always, is to always ask. We don't need to 'always' ask to nullify this problem. 'Often', or even 'sometimes' is more than enough, since we won't be bidding a lot here anyway. I don't understand that. If you sometimes, but not always ask you create a recognizable pattern of behavior (UI). I don't think so. I ask when I need the answer. And I ask sometimes at random, when I don't. Unrelated to my hand. That should be sufficient noise to throw partner off. If it were a situation where I would tend to need the answer quite often, like (1NT)-2♣* I would change questioning strategy, but that's another discussion. Theoretical, sure it would be ideal to ask always about any bid, but that is not really practical.

Favorable for a save, otherwise a lead director for the suit below. The answer, as always, is to always ask. We don't need to 'always' ask to nullify this problem. 'Often', or even 'sometimes' is more than enough, since we won't be bidding a lot here anyway.

Why is 3♥ 'clear'? It's not an invitational bid, so he is not going to raise just because he has two aces or one ace and the ♥Q. He will need overall good cards + fit as well. If we take the realistic view that our passed hand partner is not going to find a raise to 4♥ a significant portion of the time (when he can't raise 2♥ to 3) then there is only the risk left by bidding 3♥ instead of 2♥.

1NT. Reminds me of an all time classic remark from one of my team mates. "1♣ made?, did you really defend 1♣?, how did the bidding go?" :)

What does 3♥ show? It should be six hearts almost always, since there is no need to bid so high with only five. When we have five, then RHO usually just has his bid with some random four-carder so we should anticipate a bad break and partner having only three and therefore give full weight to suit quality in our choice between 2♥ and X->2♥.

This hand is perfect for 2♥ over 1♥. X then 2♥ shows five hearts too but a stronger hand.

Is such an inference legal?

It is reasonable to play 1♦-1♥-4♦ as a strong 7-3.

I really don't hope so, since that would be a horrible reason not to raise. We are not respecting partner when we are being blindly obedient to him, whatever the situation, but rather when we try to always make our best possible evaluations and act consequently on those. Partner can't see our cards for us, only we can. And leading partner's suit 'when in doubt' is bad also. ;) Ok, I guess it depends on when we are in doubt. But leading partner's suit without really thinking is bad, at least.

Result merchants will never get really good at this game for sure.

I like rogerclee's suggestion. Only adjustment I would make is to play any 3x as preemptive. 'Nobody' around here plays this "Polish 1NT" anymore, as it is being called here. So my partner and I don't really have a defense to it. We would have to fall back on normal (for us) principles when only one suit is known: D takeout, new suit forcing, their suit = good raise, etc. I would therefore have bid 2♠ in comfort as 10+ with 5+ spades. I will suggest rogerclee's defense next time someone plays this convention against us.

4♠. Have to be practical sometimes. Or is it partner's responsibility to kick it in with Qxxxx, KQx, xxxx, x or Jxxxx, xx, AKxx, xx? It's a vuln game, we just need thirtysomething percent.

Prefer double, but I can live with pass. I think double works a little better in competition, since it gets our values in immediately. The actual sequence exposes one of the downsides with pass. Yes partner bids when we have a game, great, but how are we ever going to play 3♥? We have to raise partner to game now for sure but it may cost the plus score if he is not so strong. This dilemma will arise every time partner bids volunterily again. If we double to start with, partner can here bid 3♥, which we can pass, or 4♥ by himself. We have a reasonable dummy regardless since our points rates to be working. I can understand criticizing having only one heart for acting now, but I don't understand criticizing the honour location. Having the queen of hearts is a great asset if partner should repeat his suit or whatever he bids. Yes ♠JTx looks soft, but even then we might belong in 3NT.

4NT then 6♦. I do think it is odds on to bid slam. On this bidding there is no particular strong reason to place each of the vital cards ♣A and ♥K in the opponents' hands rather that with partner. LHO is preempting and RHO is a passed hand. Also we are not dead when partner has neither of the two. Singleton heart and diamond support will often be enough. Or we could take a heart finesse if partner has ♦J. And the opponents might misjudge and sacrifice in 6♠. Many ways to win.

For us a false Q-ask and then a follow up sets focus on "something" that can't otherwise be clarified. First priority are kings that can't otherwise be shown. Here, if asker bids 5NT then the whereabouts of ♠K is lost. A false Q-ask would therefore set focus on ♠K so teller should have ♠K to make a positive move over the delayed 5NT (or compensating tricks outside spades of course). However, this specific situation we solve by having 5♠ and not 5NT as the general grand slam try in this sequence. That gives room to clarify ♠K by a 5NT-response to 5♠. Therefore a delayed 5♠ would instead, as second priority, launch queen-showing instead of king-showing. (If opener happens to have an un-shown king, he can bid it also, expecting partner to be missing only 1 of the top 3 honours in the suit anyway.) Sample sequences: 4NT(♥) - 5♣, 5♠ = general grand try, asks for kings 4NT(♥) - 5♣, 5♦ - 5♥, 5♠ = general grand try asks for queens and kings mixed 4NT(♦) - 5♦ - 5♠ = general grand try, teller can show ♠(5NT) or ♣ king 4NT(♦) - 5♦, 5♥ - 5♠(first worst: no Q), 5NT = general grand try, "but I need the ♥K" - the card that can't be shown in the above sequence.