deleting splitting regions needs automatic line de-reassociation
If one deletes a region, the lines associated to it should be automatically disassociated from it. If one divides a region into two (or more) all lines in it should automatically be reassociated to the line in which their central point is. Any other behavior is counterintuitive and will cause great confusion with users also because it is not shown in the UI that these lines are still associated to a ghost or to the wrong region. I call this a bug and not a feature request as it is unwanted behavior.