Jesus said it best "For everyone to whom much is given, from him much will be required" Luke 12:48. When someone forgives you they have given a lot and yet a lot may be required yet of you, He says.
This is true of Salvation as well. Jesus death on the cross paid for the sins of the whole world, yet much is required. Living a life of giving and love, where there was no giving and no love, is called for. Forgiving graciously where you never forgave like that is required (not that it affects your salvation but that it is evidence of Salvation).
He also referred to this in Luke 3:8 "Therefore bear fruits worthy of repentance", repentance bears fruit.
Therefore, I would respond to the Rabbi that I will go retrieve as many feathers as I can and live a life of repentance and do the opposite - lifting those in authority up and in Prayer whenever I can.
To me the impossibility of bringing back the feathers compares to the impossibility of bringing a slander back. Once out in the world, it just keeps going.
It is just like the children’s object lesson of putting the toothpaste back into the tube.
Once the words are out there, they can never be retracted. Even the Bible says the important thing is not to say them in the first place.
There is forgiveness, there is repentance, but there are also consequences.