I go with the ones that say coupling could be good or bad. Sometimes the shelf could vibrate more,and cause more problems.Coupling to something with more mass,or isolation, may help.I think it's situation dependent.
Vibration Theory - Isolate or Drain?
Given that a CD Player or Transport has quite a bit of internally generated energy from the motor, is it best ti deal with vibration issues by coupling the player to a surface with spikes or cones? or decouple the player from the surface beneath it with spongy materials? Any consensus on the best approach here?