Data structure has nothing to do with it. If you stored social media users as fake AUTHORS lines in a git repo, that still wouldn't make you allowed to keep it. In the inverse situation, storing git authorship in the comments table of your photo site's database, you would be allowed to keep it for legal uses.
I interpreted the original posters point that the git repository could not be modified without destroying it. I thought that's how the next poster was responding to it. If you cannot modify an old entry without destroying the integrity of your system, are you required to modify? Either the answer is yes and you effectively cannot use certain data structures (with their integrity) or the answer is no and certain data structures allow you to keep data.
I agree and understand, but it does give us a likely unintended consequence: no sequential hashed data structures when you are required to be able to modify it. Probably a good thing for hearing less about blockchains!
