Well, the article’s focus is on asynchrony. Naturally then, it talks about closures within the context of asynchrony and to the extent that it is relevant.
The author could have made the topic about closures, but that’s not what they wanted to talk about.
The interface also allow to comment, post and interact with the original HN platform. Credentials are stored locally and are never sent to any server, you can check the source code here: https://github.com/GabrielePicco/hacker-news-rich.