add_filter('wp_insert_post_data', 'initiate_sectionize', 99);
function initiate_sectionize($data) {
    $processed_content = sectionize($data['post_content']);
    if(is_array($processed_content)) {
    $data['post_content'] = $processed_content[1];
    add_filter('redirect_post_location', 'sectionize_location_filter', 99);
	}
    else {
    $data['post_content'] = $processed_content;
    }
  return $data;  
}

function sectionize_location_filter($location) {
  remove_filter('redirect_post_location', __FUNCTION__, 99);
  $location = add_query_arg('message', 99, $location);
  return $location;
}

add_filter('post_updated_messages', 'sectionize_messages_filter');
function sectionize_messages_filter($messages) {
  $messages['post'][99] = 'Something went wrong';
  return $messages;
}