i cant believe that it needs to be explained why chatter sound may cause damage to your turbo. but here it goes.

chatter sound becomes when compressed air flows back to compressor wheel, when throttle plate cloces. when that air flows back to compressor wing, it will make it momentarily imbalance or tremble, i dont know how to explain that in english, but anyway, the forces between compressor and turbine wheel is greatly diffirent when the compressor wheel isnt rotating freely, and that happens when airflow is pushed back to compressor. and when it spins like 100000rpm per minute, you dont have to be rocket scientist to know that it isnt good for your turbo. DV prevents the air from flowing back to compressor wheel.

forces that create imbalance between compressor and turbine wheels, are greater in hi boost(Mass, Velocity and pressure), and it is surtain, that the damage will occure in greater amounts and in shorter time, when you have hi boost.