If the main purpose of topic tags is to allow filtering and aggregation, the tags don't need to be that visible/prominent in the first place.
I'm not saying this is the answer either, because I don't know if it's a great fit for HN, but managing and verifying such tags would fit well into somethingkme the ol' the moderation and Meta-moderation systems from Slashdot.
(Using LLMs to generate initial topic tags once per article instead of having independent implementations burn up compute over it dynamically also seems like a way more reasonable way to use them toward this end.)
If the main purpose of topic tags is to allow filtering and aggregation, the tags don't need to be that visible/prominent in the first place.
I'm not saying this is the answer either, because I don't know if it's a great fit for HN, but managing and verifying such tags would fit well into somethingkme the ol' the moderation and Meta-moderation systems from Slashdot.
(Using LLMs to generate initial topic tags once per article instead of having independent implementations burn up compute over it dynamically also seems like a way more reasonable way to use them toward this end.)