Note that even in this case, you can remember that you decided to forget, as a key premise of Datomic is that you always know how and why you came to record (or forget) a fact.
Alright, that makes sense. Now it is interesting how the fact that you decided to forget would work. I guess if one always accesses the data via the official API and at the latest known state, that will work. But presumably the data will still be in stored in binary form in the back-end.
Another perhaps related question, does one have the option to "travel in time". Say I record that I forgot my mistakenly added passwords. But an attacker knows when that happens. Can they go back and inspect the data state right before the point when I forgot the data?
What you're describing is plain ol retraction. If you retract your credit card number, then someone can just surf back in time to grab it. That's why you'd excise it.
Note that even in this case, you can remember that you decided to forget, as a key premise of Datomic is that you always know how and why you came to record (or forget) a fact.