Insufficient 1NT overcall
South (dealer) opens 1NT. West bids 1NT. West wants to replace 1NT with a double.
Both sides play a weak NT, and EW plays 1NT overcall is strong, and (1NT)X as a strong NT (or better)
Scenario 1: West did not see the opening bid and intended 1NT as an opening bid.
Scenario 2: West saw an opening (1-level) bid and intended 1NT as an overcall.
Scenario 3: West says nothing and nobody (including TD) asks West's intention.
If it matters, West has a poor 15 count which would open 1NT.
Is "strong 1NT overcall" a " possible meanings attributable to the withdrawn call" (Law 23A2); and so Double is a comparable call and is therefore permitted and does not silence partner.
Comments
One of the things I struggle with on law 23 is the meaning of "attributable". How obscure can you go?
Further muddying the waters, the laws (correctly, IMHO) make no reference to the intention of the caller, yet the commentary to the laws does the opposite ("The TD might also need to ask the offender what he meant to do when making the insufficient bid.")
I'm not sure there is sufficient clairty in the laws to answer Robin's excellent question.
I think so (except possibly in Scenario 1), but ...
... that wouldn't follow, would it? The condition seems to be the wrong way round: double has a wider range of possibilities than the withdrawn NT bid (because double includes stronger hands, and also unbalanced hands). So it's not a "subset" (per 23A2) and wouldn't be a comparable call regardless of what you think the withdrawn NT bid meant.
"Further muddying the waters, the laws (correctly, IMHO) make no reference to the intention of the caller, yet the commentary to the laws does the opposite ("The TD might also need to ask the offender what he meant to do when making the insufficient bid.")"
I'm not sure that "make reference to" is really the opposite of "make no reference to", but I think the point of asking the offender what they meant to do is to add to the collection of attributable meanings. It's not otherwise a requirement for the TD to know what the offender had been intending.