IP addresses are deemed personally identifiable information. All web servers log these by default - before asking users for permission to do so - and are therefore, bafflingly, about to become illegal.
Also, I can't help but notice that currently there is a hell of a lot of money being bet on immutable public ledgers.
But you generally cannot build a system that intentionally does not have a certain capability and then successfully claim that laws don‘t apply to you, because your beautiful system does not accomodate them.
The more specific answer is:
git config --global user.name "Your Name Comes Here"
git config --global user.email you@yourdomain.example.com
Also, looking up, you can undo a rebase with reflog, so even editing commits with an interactive rebase may not be enough to purge a git repo of identifiable information that people have entered.
I've been pondering the same thing. You have to be extremely careful about building a new product on blockchain technology, because, depending on what you're building, you may be required to delete stuff from it in the future.
The tricky situation is when someone puts personal data not about themselves, but about a third party into a public ledger...