Task::addComment

public function addComment($authorId, array $data)
{
	$fields = array(
		"ANCILLARY" => true,
		"POST_MESSAGE" => $data['text']
	);
	if(!empty($data['fileId']))
	{
		$fields['UF_FORUM_MESSAGE_DOC'] = array($data['fileId']);
	}
	elseif(!empty($data['versionId']))
	{
		$fields['UF_FORUM_MESSAGE_VER'] = $data['versionId'];
	}

	// todo: move to \Bitrix\Tasks\Item\Task
	$task = \CTaskItem::getInstance($this->entityId, $authorId);
	if ($this->canRead($authorId))
	{
		\CTaskCommentItem::add($task, $fields);
	}
}