I think tagging on HN is an idea whose time has come. We already had informal tags for "Show HN" and "Ask HN" for some time. A few fixed tags chosen at submission time might suffice, for example:

- Global news, AI, Software, Hardware, Explainer, Tech Opinion, Personal project, Misc.

There could even be fake tags like Politics that trigger a message about appropriate topics.

It does increase moderation burden for mislabelling, and introduces another nitpicking point for comments to latch on, so it's not all upsides.

I'd be ok leaving filtering and other UI concerns to extensions.