I think tags/categories would be a great idea. For example, my favorite topics are the "Ask HN" ones, so it would be nice to be able to see just these by click

I think tags/categories would be a great idea. For example, my favorite topics are the "Ask HN" ones, so it would be nice to be able to see just these by clicking a tag. Same thing goes for hiding all topics tagged "Apple". Even if the tags were "hard-coded" it would be useful to have say: Ask HN, Rate My App, Tech News, Acquisitions, Job Postings, Hacker Tips, etc...