Alright, I'm going to be a real pain in the arse here and throw some edge cases at that idea - not because I'm trying to be a cockwaffle (I can manage that all by myself), but trying to straighten out my understanding of these things...
In short, what criteria does the data have to meet to make it immutable, and can that be changed in future?
Birth certificates are brilliant for establishing time dates and places, but what if someone changes their name or gender partway through life? Is there a function to amend the original blockchain entry, or is a new one created that supersedes an old entry in the ledger?