Why can’t I follow or favorite a HN user?

I would argue that follow/fav will turn HN into a other kinds of social media?

You want to hear/read interesting topics, comments and voice your opinion. While reading the favorite person's comment is really good, I don't limiy myself to that.

I normally go to NEW tab rather than just home page and to ASK tab occasionnaly.

Follow/Fav might just ruin my homefeed making me bias.

You can... the old fashioned way. Just bookmark a user's page and remind yourself to check it from time to time.