Why is it bad to rest my hand on the shifter knob?
When you rest your hand on the shifter, you are loading a bronze transmission component (called a slider) against steel components, either the blocking ring or the gear stop. This will cause accelerated wear on the softer-metalled blocking ring, which will soon lend itself to popping out of gear. It can also cause an overheated gear from the additional loading. This will not show itself until fatigue breaks it. Unless you are shifting the car...don't touch it.