ESC dampening is a great feature to have in the Blheli firmware. It enables faster throttle responses by braking the motors when dropping the throttle to a certain value.
Unlike conventional ESCs with SimonK firmware ( our preferred Blheli ESC firmware ) , the motors have to spool down from the drag or the propellers to reach the lower throttle level. This causes difficulties in tuning since at lower throttle, PIDs is decreased, and the propellers travel down into its own prop wash (air turbulence from itself) which is results in nasty shakes and oscillations.
Dampening is also beneficial for tricks and flips since the aircraft can cut the throttle instantly allowing sharper control and less drifting caused from the spooling of the motors.
What does dampening actually do?
If you haven't figured out what dampening does, it adds resistance to the motors when the throttle is dropped. This is like applying the brakes to a speeding car whereas SimonK lets the car roll to a stop. Switching to Blheli with dampening, I can say with confidence is a guaranteed easier tuning for beginners since you remove natural oscillations like prop wash which I mentioned above.
A unique characteristic of dampening is that the motors continue to keep their resistance even when the lipo is unplugged. The resistance reduces after a few minutes. If you want to know for sure, use Cleanflight ESC's pass through to connect to your ESCs and check if it is enabled in Blheli settings.