Bluesky API currently requires authentication to the app.bsky.feed.getPostThread endpoint, which is used to load complete threads.

At the moment there is no way to log in using OAuth, only with a password. The password is only passed to the Bluesky API and isn't saved anywhere. The returned access token is stored in local storage. You can create an "app password" in the Bluesky app settings that you will only use to log in here.

You can see the complete source code of this page on GitHub (and in your browser's web inspector!).