Well then, there's an excuse to book another track day
As I visualise it, if something is occilating between two points (chatter), the way to stop it doing so it to dampen it (more). If it can't occilate as quickly then the frequency will change and lessen the chatter.
But on these new fangled shocks with high and low speed damping changing the high speed damping would seem the way to cancel it as chatter is a high speed movement (all be it over a small distance)
Fiddlin' time!
C