Hacker News Reader

I have noticed the same thing and wholeheartedly agree with you.

Simple solution: categories with separate feeds.

That leads to the subreddit problem.

Solutions to problems lead to more problems.

How about instead of having the submitter categorize the submission, everybody can categorize it, just the same as everybody can upvote?

Not sure what "the subreddit problem" is. Just wondering if that would help.