[mycroft]

Why are you the only one? Probably where you play.

First, there's the one that plays a strong NT. Whether they learned somewhere else, or have been convinced to join "the modern world", or whatever.

But it's likely that most of the rest play a weak NT because that's what they learned (mumble) years ago, and their system hasn't changed since. And back in the day - especially in an Acol, rather than K/S context (this is NZ, not Canada, so I assume a British Bridge background) - what Tramticket was taught was what was taught (4cM, so ♥AKxxx is obviously rebiddable). Whether they've moved away from 4cM or not, the feeling hangs on.

Sure, Tramticket has moved on from there, but he is a serious student of the game, and is willing to change and work on change and evaluate change if it makes things better. He's here, after all (and his comments for years make it clear). Many - if not most - club players haven't changed fundamental parts of their system since they started playing with that partner - or if they did, it's one of the standard two (SA to 2/1 GF in North America, 4cM to 5cM in RoW (and if they're really old, in NA too)). And 40 years ago they would never have opened that hand 1NT, so they don't now either.

I'm a strong proponent (in some partnerships; oddly enough, my K/S partnership isn't one of them) of 5cM in NT. But I too am leery about this one with the minors wide open and with an acceptable 2♠ raise (assuming you'll do that with 3 ever, AJx and a weak doubleton is a prime candidate).

[helene_t]

Most New Zealanders play weak NT and 4-card majors. So
1♥-1♠
1NT*
is typically 15-17 balanced with four hearts. With that shape you don't have the option to rebid 2♣ like you might do with a 2533 16-count if you played the 1NT rebid as 12-14.

Another thing is that
1♥-2♣
2♥*
is nonforcing for most of those weak-NT playing New Zealanders. This is because a balanced 16-count with a 4-card hearts would have to pass a 1NT response, so the 2-level response can be done with as little as a good 9-count and hence has a low forcing character. When rebidding a suit non-forcingly you would like to have a suit that plays well with doubleton support and not ridicolously badly with singleton support.

So what I am trying to say is that especially in a weakNT/4cM system there is a really good case for opening 1NT with a 5M332. The argument goes

Weak&4M -> 1NT-rebid must include (promise?) 15-17 bal -> a 5M332 minimum doesn't have a good rebid if opening a suit

and

Weak&4M -> 2level shift can be light -> 1M-2m-2M is nonforcing -> better open 1NT to avoid this

Of course, there can also be good reasons for opening 1NT in Weak&5 system, but it is somewhat less imperative I think. However, if you play forcing 1NT, you don't want to have a 5M332 minimum when it goes
1M-1NT
2m-3m

[Tramticket]

helene_t, on 2023-March-14, 11:45, said:

the 2-level response can be done with as little as a good 9-count

I can't comment about New Zealand, but in the UK, the modern tendency is to require a 10-count. Yes, a good 9 HCPs might be upgraded to 10 on occasions, but one of the most important factors in choosing to upgrade should be a useful holding in partner's suit. Whilst 1H-2C-2H is non-forcing, responder will make every effort to find a second bid - particularly if very short in hearts. 1H-2C-2H isn't passed out very often and I can't remember ever playing in a 5-1 misfit on this auction.

I do agree with Helene, that the specific 2533 shape is an awkward 1H opening, because you can't raise a 1S response, 1H-1S-2H really should promise a six-card suit and I would be very reluctant to bid 1H-1S-2C with a three-card club suit. I would generally open 1NT with this specific shape.

[Cyberyeti]

Tramticket, on 2023-March-15, 02:46, said:

I can't comment about New Zealand, but in the UK, the modern tendency is to require a 10-count. Yes, a good 9 HCPs might be upgraded to 10 on occasions, but one of the most important factors in choosing to upgrade should be a useful holding in partner's suit. Whilst 1H-2C-2H is non-forcing, responder will make every effort to find a second bid - particularly if very short in hearts. 1H-2C-2H isn't passed out very often and I can't remember ever playing in a 5-1 misfit on this auction.

I do agree with Helene, that the specific 2533 shape is an awkward 1H opening, because you can't raise a 1S response, 1H-1S-2H really should promise a six-card suit and I would be very reluctant to bid 1H-1S-2C with a three-card club suit. I would generally open 1NT with this specific shape.

Are you really not bidding 2♣ and passing 2♥ with say xxx, x, xxxx, AKQxx (add a non club jack if you'd bid 1N on that) ? It can happen but you're right it doesn't happen that often.

Otherwise I agree with most of what you say. The important agreement is that you never pass 2♥ with 4 unbid spades, so you respond 1♠ with the 4135 version of that hand. The downside of this is that the raise to 2 ♠ on the original hand is more likely to be a 4-3 fit.