What actually should happen is that they are reopened and closed as duplicate again. Then the banner can be removed from the body. The reason for that is the automatically inserted duplicate banned that used to be added to (alleged) duplicates.

Since quite some years now the banned is separated from the actual body, so the question title will be updated automatically too when it changes.

I have done it for the one question with a tag I have a gold badge in.

What actually should happen is that they are reopened and closed as duplicate again. Then the banner can be removed from the body. The reason for that is the automatically inserted duplicate banned that used to be added to (alleged) duplicates.

Since quite some years now the banned is separated from the actual body, so the question title will be updated automatically too when it changes.

All done now.