Wait maybe I’m missing something, but are you saying the temporary confusion while people realize they have different versions would be the primary downside? I feel like that’s an acceptable loss. It seems likely that the data in both commits, while one healthy and the other corrupt, will still have to be very different in order to produce the same hash. It’s not like you can reasonably find same-hash commits that just change line19 execute_hack from true to false.
The commit message is part of the hash. You could have quite a lot of entropy there which wouldn’t get much notice until the postmortem.