I'm sure I remember reading somewhere ages ago that when unsubscribing from a mailing sent to a parent group, the contact would be removed from all of the child groups that they belong to that are under that parent group.
Has anyone got a reference for this expected behaviour when this functionality was put together/documented?
My personal view is that it would be better if they were only removed from the parent group. Being removed from the child group would seem to break any hierarchical group mailing system that an organisation has setup.
Note, this is a follow up to the issue https://issues.civicrm.org/jira/browse/CRM-19924 "Unsubscribe from a mailing sent to a parent group silently fails" i.e. currently nothing happens at all when a user clicks an unsubscribe link sent to a parent group.