Starting from Confluence 6.13, admins can delete users that are unsynced from Confluence. Unsynced users are users that are not synced any more when an external user directory is being synchronized. This could be because the user has been removed from the external directory or it is because the user directory filters no longer include that user etc.
While this feature is useful, the current implementation only allows the deletion of these users individually and there is no option to perform bulk delete.
Having the bulk delete feature would greatly help.