Frank Herbert would be proud!
I cut the tip of my thumb off and it grew back perfectly complete and normal.
I’ve also had *lots* of nasty cuts as a kid that technically should’ve gotten bunches of stitches but I never did.
I also survived a head injury that destroyed my whole frontal lobe.
There used to be an “empty space” there but it’s grown back.
There are no scars on me whatsoever, even where the accident sheared off the top of my ankle bone.
[I am not, however available for experimentation]
regenerative medicine/stem cell ping