By design nothing in the chain can be altered. But of course you could have a block indicating “person X is now person Y”. But you can always read that Y was at some point X (and at what point the change happened). That would not be good, as it would be a public ledger of all trans people. It would also make things like witness protection impossible because inserting a block “today in 2024, person W was born in 1974” is very suspicious