Originally Posted by FBinNY

This is only true to a limited extent. Aluminum isn't taffy, and won't stretch beyond narrow limits. Once it reaches a point on the taper the force needed to move it farther becomes staggering. In some cases it's possible to move a left crank far enough that the radial force of the taper cracks it. But it's extremely rare that a right crank can be tightened enough to be damaged.