Groupblog comments and deletion notifications
TODO for the groupblog / XEP-0060 plugins:
- comments node must belong to the main_item publisher. Check what is happening with the auto-create feature, the node must not belong to the first one who add a comment.
- as deletion notifications are not working well, it is possible to post a comment for a main_item that has been deleted. In that case the comments node is re-created with the auto-create feature, it should fail instead.