AL78, on 2022-September-05, 04:42, said:
Bidding NT has the advantage of narrowly defining the hand and allowing responder to take charge. The disadvantage is if responder has a minimum response with diamonds and hearts, they will pass and miss a potentially superior 2♥ contract.
Which is why so many people play a style which bypasses diamonds to bid hearts these days with weaker hands, because we care about missing heart fits a lot more than missing diamond fits.
Responder with 18 is really bad to just jump to 3nt regardless, as 1H is wide ranging, could be some unbalanced hand just short of a jump shift. They should go through whatever artificial forcing mechanism they have, and bid slam if partner now shows extras in NT, or invite slam in NT (bid a forcing 2nt then 4nt).
The biggest problem is playing this way when responder has like 9/10 pts not 18. The auction starts something like 1c-1d-1h-1nt, responder being not quite strong enough to invite opposite a min distributional hand. But opener with 15/16 can't know if responder is closer to 10 pts where you want to be in game or 6 pts where 1nt is quite high enough. Thus why weak NT people tend to play a style where the strong NT rebids 1nt.