Stephen Tu, on 2019-April-05, 06:09, said:
There is a language barrier; it is not clear exactly what questions you are asking about the convention, exactly what you want discussed, that is why you have been posting by yourself.
I think most experts agree that it is useful to have a low level forcing raise of a major. If you look at convention cards for something like say the Rosenblum, you find that almost everyone is using 1M-2nt as some sort of raise. Normally it promises 4+ trumps, but is more often balanced than unbalanced; as unbalanced hands often want to describe themselves (by splinter raise, or 2/1 in a suit followed by support), rather than enquire.
The main variance I see is whether it is game force, or also includes invitational hands (in which case it probably no longer qualifies as "Jacoby").
Everyone agrees that the "standard", original Jacoby 2nt response structure is very inefficient, revealing too much about opener shape when both parties minimum and slam will not be reached, and being space inefficient otherwise. So many improved structures have been devised and you can search either here or bridgewinners or internet in general to find better ones.
I don't understand pescetom's comment about Jordan 2nt. Jordan 2nt usually refers to 1M-dbl-2nt as opposed to 1M-p-2nt. Here most play this as LR+ even if without double they play 2nt as GF.
What I did (and then I discovered to have been thought of also by A. Gumperz: see this answer in Limited bidding ....:"Hendrik SharplesI've been using 3C as stiff / void 11 + -14- or 17+, 3D stiff 14+ - 17, and 3H as minimum, figuring we need room to sort out the shortness, and rarely need delicate tools 4 out of the major show 6 to AKQ or at least one out of control. We can't use 2NT as LR plus with this structure Have you had any experience with using a higher step for the minimum balanced?
May 11, 2012

Andrew Gumperz
I have not. When it is clearly the limit. I specifically want to separate the balanced and unbalanced mins with my first response for that reason.
I agree with you that you are less balanced, delicate tools have less value - you are going to require either a stiff or a mountain from responder. I also like the idea of 4M as a picture bid - a trump heavy opener
May 11, 2012") is to separate the hands between balanced and unbalanced. In this way: both for the one and the other distribution the response range is 14-18 1M-3M forcing only for the three balanced ones while for the unbalanced (1M-2NT)ones also including the 5-4-2-2 the answer is used 2NT Jacoby and the four basic answers.