SUMMARY
Add the ability to mark a face region as "Ignored".  This removes the face region from the "Unknown" group without giving the face a specific name.

In a simpler implementation, ignored faces are not processed for recognition.

In a more complex implementation, ignored faces are automatically grouped by close similarity and assigned an internal name.  Face recognition will consider these groups as people and offer them as a suggested match for other images, using "Ignore" as the suggested name.

ADDITIONAL INFORMATION

This is important when re-scanning images for faces.

By marking faces as Ignored, you indicate that they do not need to be reviewed again.

Deleting the face region is not a substitute, as the face will be re-detected with a subsequent scan and again marked as Unknown.