[@wpturk Participant 3 years, 7 months ago]

This should do the job: (put this in your functions.php)

function bb_auth_reply_view( $reply_id ) {
        $reply_id = bbp_get_reply_id( $reply_id );

        // Check if password is required
        if ( post_password_required( $reply_id ) )
        return get_the_password_form();

        $content = get_post_field( 'post_content', $reply_id );

        // first topic reply shouldn’t be hiding
        $rep_position = bbp_get_reply_position($reply_id);

        // if user is not logged in and not the first post topic
        if( !is_user_logged_in() ) {
                return "Replies only viewable for logged in users";
        } else {
                // return normal
                return $content;
        }

}
add_filter( 'bbp_get_reply_content', 'bb_auth_reply_view' );