Marc, I agree. If they say informal, it is quite clear what the requirements are, jacket, but tie optional. Maybe the Bermuda cruises will be the next CCC full cruise. However, on the Diamond in January in the islands, we had a formal night. In Alaska, I think every other line has formal nights but Radisson.
I agree also with gopack. Most of the "moaning and groaning" about dress code seems to come from men! (at least in my memory of this subject). But then, if I had to wear a tight thing around my neck in hot weather, maybe I wouldn't like it either. There is always talk of extra weight in the bags for formal (from men). For me, my formal stuff is lighter per outfit than ccc, when I may bring a pants suit and blouse instead of one little lightweight silk dress.