BuddyPress.org

It depends on how you’ve defined your moderators.

On one of the sites I’ve worked on, each moderator was a site admin, so I did a check to see if the user is a site admin and applied a badge on the avatar.

If you don’t want to give site admin access, you can probably change each user’s role to an editor in WP, then do a check to see if they’re an editor.