The "favorites" feature is amazing and just rightly inconspicuous. On my website, https://mihir.ch/#hn, I've been collecting and displaying my favorited posts and comments from an API I created for this purpose only.
The API: https://hn-faves.now.sh
The API: https://hn-faves.now.sh
Usually I'd use puppeteer, but that would make it like 400mb. I've never heard of [1] x-ray, it looks a great package for lightweight containers!