You don't understand the problem. You can drive the pin back into the chain on SRAM or Shimano. But that doesn't prove anything. The pins on both sides of the chain are expanded during the assembly process to stand up to the side forces and thiner plates for chains used on systems with 8 gears or more...perhaps even 7. When you push out the pin, you get rid of that expansion and the pin won't hold. It may take a while but you are risking a chain breaking by using the old pin.