mw.notifications are currently really small and honestly hard to notice. They could be improved to have icons like checkmarks or X's on Desktop. Additionally, we have a second notification system for postEdit (and it differs in visual style for a researched / ab-tested reason).
Both systems could use a bit of a visual make-over to bring them into 2015-16.
Additionally, templatesthe two systems should probably be combined/share an api, be bigger,to make it easier to target them on mobile and other different skins. etc. postEdit is also basically a notificationAnother possible usecase is for user-user messaging and other 'in page' website notifications that we currently do not yet provide but have been discussed.
The notifications could be improved to have icons like checkmarks or X's, templates, so if we could improve notificationspositionable and to look as good as postEdit boxes we could combine the two.have different 'attention' levels towards users.