WP_REST_Comments_Controller::get_item_permissions_check

	public function get_item_permissions_check( $request ) {
		$comment = $this->get_comment( $request['id'] );
		if ( is_wp_error( $comment ) ) {
			return $comment;
		}

		if ( ! empty( $request['context'] ) && 'edit' === $request['context'] && ! current_user_can( 'moderate_comments' ) ) {
			return new WP_Error(
				'rest_forbidden_context',
				__( 'Sorry, you are not allowed to edit comments.' ),
				array( 'status' => rest_authorization_required_code() )
			);
		}

		$post = get_post( $comment->comment_post_ID );

		if ( ! $this->check_read_permission( $comment, $request ) ) {
			return new WP_Error(
				'rest_cannot_read',
				__( 'Sorry, you are not allowed to read this comment.' ),
				array( 'status' => rest_authorization_required_code() )
			);
		}

		if ( $post && ! $this->check_read_post_permission( $post, $request ) ) {
			return new WP_Error(
				'rest_cannot_read_post',
				__( 'Sorry, you are not allowed to read the post for this comment.' ),
				array( 'status' => rest_authorization_required_code() )
			);
		}

		return true;
	}