Moderation since 1.15.1
This feature could be enabled in Admin > Settings > Enable Moderation. By default it is not enabled.
Report an event
When this feature is enabled (Admin > Settings > Enable Report) every person could report an event.
All administrators will receive an e-mail notification with the report.
This feature is not enabled by default. Note that to enable this feature moderation should be enabled too.
Manage a report
Admins and editors could talk each other and take notes on events, eventually they could send some message to the author of the event too.