Reflective Immutability

Would you rather have Immutability or Reflective Immutability?

After reading Reflective Immutability, how powerful is it? How would someone potentially gain this? I find the power interesting, hence why I ask.

What would happen to let's say SCP-073 if he was shot in the head with a sting-embued arrow by Flechette from Worm?

Would Flechette's attack actually go through?

How about other characters with this ability? Like for example the Dolly Dagger from JJBA? Would the amount of damage received be 100% rather than 30% due to the nature of the Sting shard?

I know that King from Worm was one-shotted when Flechette hit him.

Just wanted to hear people's thoughts. Thanks!