What xvlk said.
Lower polarization means lower output level. From 80V to 48V will be noticable, but still usable.
Higher polarization increases output BUT at some point the diaphragm is sucked into the backplate, which is bad.
And when a designer has control of all factors (voltage, spacing, tension), the polarization voltage is just a little less than the suck-in voltage, and the output level in a quiet studio is just high enough to overcome buffer noise. So you never want to increase voltage, and probably don't want to reduce it very much (80V to 48V is OK).
As you approach suck-in voltage, the diaphragm stiffness is partly canceled by polarization voltage force. As xvlk says, "negative reactancy, rather theoretical..". Most mass-produced mikes don't use a polarization voltage so close to suck-in voltage that the stiffness really changes.