public boolean demoteUser(String name){ //deop a user by name
        if (name.equalsIgnoreCase("admin")) return false; //can't demote the admin
        UserAccount user = users.get(name.toLowerCase()); if (user==null) return false;
        user.setIsAdmin(false);
        if (user.getThread()!=null) user.getThread().send("You are no longer op.");
        return true;
    }