The symmetrical modelling GWeb is referring to (and Waldo did some time back, I remember) is that used in ZBrush. It is very useful in that program because of the way you can deform objects in much the same way you would model clay. There is even radial symmetry which you can set to how ever many 'pointers' you want which is a handy feature for decorating lathed objects, for example. Modelling in Carrara is geared to a different sort of modelling and I can't really see any huge advantage in using symmetrical pointers over the other methods, apart from as Eric says, being able to see better what you're doing (though Amapi allows this as has been mentioned). I'm slightly puzzled as to why GWeb won't use ZBrush for this sort of modelling, when it is one of the program's strengths and use Carrara for the sort of modelling that it is good at. Mark