There should not be a mechanism for that. China mastered such mechanisms. We should rather optimize for not having that kind of points of failure.
For the same reason I find it comforting that an old fashioned bank transfer can be corrected if I transfer money and make a mistake writing the account number. Mutable history is a powerful feature.
Once a secret is exposed to the internet, it should be considered public and rotated. In this case mutability/immutability is moot though likely there are applications for other, non-credential secrets that are not so easily rotated (like your home address or something).
In real life, there are not billions of Mallorys watching your stuff constantly. Most people are decent and most of the others are deterred by laws, and the number of people who are willing to help abusers is relatively small.
Just using some real-life examples, think about doxxing or revenge porn. It’s technically true that this data cannot provably be removed from the internet but in practice most people didn’t save it and the ones who did became a lot more covert once the legal system caught up, which means that in practice far fewer people see it. The initial damage may have been done but that doesn’t mean we should give up and do nothing because there isn’t a theoretically-perfect option.
I get that. However, it's arguable that mistakes are all too often eternal against the most dangerous adversaries, such as authoritarian governments and other criminal organizations with state-level resources. And so it's arguably better to focus on resistance to censorship.
That's not necessarily mutable history though. Such a correction will usually be made by an inverse transaction, not by wiping the original transaction from the record.
Ridgemont High.
Golden.