This is how I use stars - as bookmarks. Am I doing it wrong?
Nope. Github stars are intended to be used the way you've described:
https://docs.github.com/en/get-started/exploring-projects-on...
It's similar to a user clicking the "favorite" link on a particular HN comment. It's a way for HN users to "bookmark" old comments to be saved in their own "favorites" list.