問題ページでソースコードをデベロッパーコンソールに貼り付けると、雑なフォームが出来上がります

yosupo.js

(function(global){
	var $comment_form, $chat_form, $user_id, $token, $comment, $text, $comment_submit, $chat_submit, $section;

	var doc = global["document"];

	function create_input(type, name, value){
		var $dom = doc.createElement("input");
		$dom.type  = type;
		$dom.name  = name;
		$dom.value = value;
		return $dom;
	}

	function create_form(method, action){
		var $dom = doc.createElement("form");
		$dom.className = "pure-form pure-form-aligned";
		$dom.method    = method;
		$dom.action    = action;
		return $dom;
	}

	var user_id = doc.querySelector(".content>p:nth-child(1)").innerText.split(":")[1].substr(1);
	var token   = doc.querySelector(".content>p:nth-child(2)").innerText.split(":")[1].substr(1);

	$section = doc.querySelector("section");

	$comment_form   = create_form("GET", "./comment");
	$user_id        = create_input("hidden", "id", user_id);
	$token          = create_input("hidden", "token", token);
	$comment        = create_input("text", "comment", "");
	$comment_submit = create_input("submit", "submit", "comment");

	$comment_form.appendChild($user_id);
	$comment_form.appendChild($token);
	$comment_form.appendChild($comment);
	$comment_form.appendChild($comment_submit);
	$section.appendChild($comment_form);

	$chat_form   = create_form("GET", "./chat");
	$user_id     = create_input("hidden", "id", user_id);
	$token       = create_input("hidden", "token", token);
	$text        = create_input("text", "text", "");
	$chat_submit = create_input("submit", "submit", "chat");

	$chat_form.appendChild($user_id);
	$chat_form.appendChild($token);
	$chat_form.appendChild($text);
	$chat_form.appendChild($chat_submit);
	$section.appendChild($chat_form);

})((this || 0).self || global);