The global feature flag ShortLived.EnableUserNotifications is exposed in Domino v5.0.2 but has no effect. The new User Notifications system is a 5.1 feature and in 5.0.2 this flag has no effect.
The feature flag was accidentally exposed in Domino 5.0.2.
The new global User Notification system is on by default in Domino 5.1 and this flag will be set to true by default. Documentation on this feature is located here: