Source

File: wp-includes/rest-api/endpoints/class-wp-rest-comments-controller.php

protected function normalize_query_param( $query_param ) {
		$prefix = 'comment_';

		switch ( $query_param ) {
			case 'id':
				$normalized = $prefix . 'ID';
				break;
			case 'post':
				$normalized = $prefix . 'post_ID';
				break;
			case 'parent':
				$normalized = $prefix . 'parent';
				break;
			case 'include':
				$normalized = 'comment__in';
				break;
			default:
				$normalized = $prefix . $query_param;
				break;
		}

		return $normalized;
	}