You can go back to any note from any time and edit it everywhere?
Yup. You can also request deletion but not all relays support it.
Well, that's cool. I think most people probably mean that they want this implemented somehow at the protocol level where relays have to respect it if they want to get notes from a particular user. I imagine something like a setting that let's me not transmit to relays that haven't adopted the enforcement mechanism
I could manually choose relays, but that isn't real enforcement.