Nothing crazy about it, judging by how much CPU and memory it uses. Now, if it managed to grow features without bringing my M4 Mac with 64GB of ram to a crawl... that's be magic.
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.