CTaskCommentItem::add

static function add(CTaskItemInterface $task, $fields): int
{
	if (!is_array($fields))
	{
		$fields = [];
	}

	if (!array_key_exists('AUTHOR_ID', $fields))
	{
		$fields['AUTHOR_ID'] = $task->getExecutiveUserId();
	}
	$fields = self::formatPostDateField($fields);

        // rights are checked inside forum`s taskEntity class, NO NEED to check rights here
	$result = Comment::add($task->getId(), $fields);
	if (!$result->isSuccess())
	{
		$errorMessages = ($result->getErrors() ? $result->getErrors()->getMessages() : ['']);
		$errorCode = TasksException::TE_ACTION_FAILED_TO_BE_PROCESSED | TasksException::TE_FLAG_SERIALIZED_ERRORS_IN_MESSAGE;

		throw new TasksException(serialize($errorMessages), $errorCode);
	}

	$resultData = $result->getData();

	return (int)$resultData['ID'];
}