By critiquing the content.

I know that's not a perfect answer, but it's pretty much all we have, and the approach does have one major advantage: it doesn't need to care how veiled an ad is, or if it's an ad at all.

Thanks! I agree in a platform like HN (where readers likely have above average critical thinking skills) that can work.

I'm not as optimistic about thinking skills, because manipulation techniques seem to work anyhow. But barring actual evidence of abuse, I think we mostly can only try to get better at countering false or distorted information with more correct information.