I think we need to decide if we're talking about a socket extension, or a handle extension aka cheater bar.
I've read that a socket extension does not change the amount of torque, and since the torque equation depends on how long the lever arm is, I think that a cheater bar will change the torque characterisitcs. BUT, since the spring inside the torque wrench is what decides when it "clicks" I'm not sure if either matters....
