presumably they don't store a cookie indicating your opt-out choice because you chose to opt-out, that is a small price I am willing to pay as a reminder that I don't really need to read the article on their damn website anyway. There are multiple tech 'news' websites that are often posted on HN that I haven't read articles from in over a year. I find personal tech blogs to be much less invasive and more interesting anyway which is the silver lining to the current trend of news websites being so unusable.
