If you do get hit (or think you did)....
Feedback on Google's recent helpful content update
As you'd expect, it does state that no direct action will be taken.
But if enough of these went in, you'd have to think some sort of notice might be taken. And it may be the only recourse other than some form of drastic content review exercise.
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Edit PS As far as I'm aware, there are no reports so far of any drastic changes anywhere. I'd suggest the few reports and experiences of fluctuations in impressions
may not be related.
But note...the very fact that this feedback form has been released suggests that Google fully expect there to be notable impacts. The timing of its release may be a pointer.