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Peening material is a different process than striking hardened seel faces together with force. Peening requires controlled steel to steel contact,often with an allowed bounce of the peening tool itself,BUT the strike force is not great. Other than the risk of life itself,it is not dangerous except in the minds of some who worry about such things.
HOWEVER!! Let me also say that a sharp hard steel/hard steel blow with heavy arm strength force will indeed produce shrapnel that will penetrate human tissue with the greatest of ease. I learned this as a young man the hard way--resulting in having a thumbnail sized divet from a hammer face surgically removed from my forearm--ruined my good Plumb hammer but the Bluegrass survived.