Most reg bodys/parts are chrome-plated brass which is fairly soft. As with any thread form, over torquing will stress the material and take it into its plastic region and cause deformation - it wont return to its original form. Ideally you want to stay in the elastic region of the material to provide clamping force without deforming the thread form. It is possible to repair a stripped hole using a threaded insert which involves oversizing the hole and tapping it for the insert. Not sure that is even done on regulators though