[fromageGB]

Vampyr, on 2014-May-02, 14:18, said:

I think that wide-ranging 1NT rebids will cause more problems than they solve. For instance, after opener rebids 1NT, responder will not know whether she has an invitational hand or not, and there is the potential to end up in, eg, an uncomfortable 2NT with 12 opposite 8.

If you agree that rebidding 2♣ could also have the same range, then this has exactly the same problem.
Opening 1NT with a shortage solves the strength problem, but not many have this agreement. Or they don't disclose it.

[kenberg]

Here is a frequent problem for responder:

The other day it went 1♣-1♠-1NT. I have five spades and modest values. Partner might have raised my spades with 3, but with a flat hand he might not. I passed. Well, pard had 3. In this case 1NT made, and 2♠ would hae also made, so no problem. But still, I frequently have to decide, without all that much to go on.

After 1♣-1♠-2♣ I am far more confident that partner does not have three spades. Yes, he might, but usually he will not.

It is true that there is still the issue of strength, but if I, the responder, look at my hand and figure that we do not have a spade fit and game in clubs requires 11 tricks, I will often get it right.. Sometimes partner will hae more in clubs than I expect and, had I only known, we would end in 3NT. This doesn't seem to happen all that often.