Ah, this is so interesting! It seems like you're allowed or not allowed to keep data based on the data structure that you use to store it!

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.

You would want to avoid using a git-like data structure for data you have to delete. But the example was data that's part of making the copyright license function, and you can keep it for legal purposes.

> But the example was data that's part of making the copyright license function

You entirely missed the point of my hypothetical, which was about immutable data structures like git employs.

As it turns out, our business also uses a git-like hash-chained commit log for our normal database. Deleting old entries would thus violate the integrity of our database. Is that now illegal under the GDPR?

When, it's about being able to judge things on their specific merits -- as opposed to having some blanket one size fits all rule.

Law has nuance and cases (and corner cases), it's not some strict predicate.

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!