Naven
Glossary
Message deletion
Removing a message after sending it.
Two different features share the name: removing it from your own view, and removing it from everybody's. The second is the useful one and the one open to abuse, since it can erase a record somebody else needed.
Most platforms leave a tombstone saying a message was deleted, which is the honest middle.
Where Naven stands
Naven leaves a note that a message was unsent rather than removing the gap silently.