I think GWeb is looking for symmetrical modeling. Some packages have a little option when turned on will mirror modeling changes done on one side of the model on the other. Most packages that have it are a little more integrated than Carrara's solution or Project Gemini, showing the changes directly in the modeler. I think I've used Lightwave's version, but it's been a while.

In some implementations, the UI will actually show two pointers, and I think that is what GWeb is referring to. I haven't seen this since the DOS days when applications painted their own pointer however, everything I've seen recently just uses the windows/mac pointer and mirrors the changes, but I don't spend much time outside Carrara so this may be more common than I believe.

It doesn't seem to me to be a show stopper feature since you can do symmetrical modeling using the dupe with symmetry trick or Gemini and true symmetrical modeling doesn't allow you to create anything you couldn't create with Carrara as-is, but it is a nice to have since you don't have to watch the changes in the preview window, you get the full UI.

Regards,
Eric Winemiller
Digital Carvers Guild
3D plug-ins for Carrara
http://digitalcarversguild.com

Eric Winemiller
Digital Carvers Guild
Carrara and LightWave plug-ins