Allow Users to Share Private Events
Note:
As of the 5.1 release, private events may not be shared. So this setting is removed from Central Admin.
With Allow Users to Share Private Events turned off, there is no "Share" option in activity stream events that are private (for example, events coming from private communities or private messages). This screenshot provides an example of the normal view of a private message:
Share option missing
With Allow Users to Share Private Events turned on, a Share option is now available:
Share option available