FYI, due to time constrains just had to edit source: line 1235 on /buddypress/bp-groups/bp-groups-classes.php – display_name ASC
$members = $wpdb->get_results( apply_filters( ‘bp_group_members_user_join_filter’, $wpdb->prepare( “SELECT m.user_id, m.date_modified, m.is_banned, u.user_login, u.user_nicename, u.user_email, pd.value as display_name FROM {$bp->groups->table_name_members} m, {$wpdb->users} u, {$bp->profile->table_name_data} pd WHERE u.ID = m.user_id AND u.ID = pd.user_id AND pd.field_id = 1 AND group_id = %d AND is_confirmed = 1 {$banned_sql} {$exclude_admins_sql} {$exclude_sql} ORDER BY display_name ASC {$pag_sql}”, $group_id ) ) );
} else {
$members = $wpdb->get_results( apply_filters( ‘bp_group_members_user_join_filter’, $wpdb->prepare( “SELECT m.user_id, m.date_modified, m.is_banned, u.user_login, u.user_nicename, u.user_email, u.display_name FROM {$bp->groups->table_name_members} m, {$wpdb->users} u WHERE u.ID = m.user_id AND group_id = %d AND is_confirmed = 1 {$banned_sql} {$exclude_admins_sql} {$exclude_sql} ORDER BY display_name ASC {$pag_sql}”, $group_id ) ) );
}