Who can report? is a feature in BuddyPress Moderation Tools that allows you to restrict reporting content according to options. Please, follow Moderation->Settings->General Settings and scroll down to Who can report.

Here is a screenshot showing the Who can report options.

Only Site Members:- If you enable this option, it allows you to limit that only site members can report the content.

Visitors & Site members:- If you enable this option, it allows visitors and site members both to report the content

Demo for Limiting who can report BuddyPress content.