The incorrect merge is preserved because that is what actually happened. The incorrect merge was published. People saw it (and commented on it in the SQLite Forum). If I "disappear" the merge, that would be airbrushing history. The correct solution is to fix the problem, while maintaining an immutable audit trail, not to delete the problem.

When I was in high school, I was taught that if I worked as a bookkeeper and I make a mistake, I should never erase the mistake. Instead, draw a line through the mistake, notate what is wrong, and enter a correction. To erase an entry in the financial ledger of a company is fraud. It is a felony. Making a correction is fine. But do not erase. Always preserve an audit trail.

I believe that VCSes should be treated similarly. While you are assembling a change, you can make as many erasures and corrections as you like. But once you commit the transaction - once you check-in the change - it then becomes part of the permanent record. To alter that transaction after the fact is akin to felony fraud. Sure, mistakes happen. By all means, correct the mistakes. But the original mistake and the correction should all be part of the audit history.

If you want to say that commits to your private branches are not part of the permanent record, and that you should therefore be permitted to edit those private branches, then I think you have a stronger case. That does not come up as much in Fossil. Fossil does support private branches, but they are seldom used. The usual case in Fossil is that all check-ins auto-sync up to the parent repo.

Shunning is not quite the same. Shunning is a mechanism for removing illegal are illegitimate content. Shunning is sometimes required to comply with legal mandates. But it is not a part of day-to-day practice. Shunning is an exception - and escape valve - undertaken only in an emergency.