I would argue that it wasn't so much 'engagement for the sake of engagement', as the content was at least relevant, and more engaging (at least to me) than a repost of whatever Techcrunch published that day. Or another political argument which inevitably devolves into whether capitalism is the problem or anarchy is the solution. Or bikeshedding over languages, or paranoid conspiracies about the American Racist Surveillance Hegemony. Or sexism in tech. Or why if you're not y, then you're x.

Most of the reasons dang put forth as to why he killed those particular threads could be applied to almost every thread on this site - depending entirely on the opinion of whomever happens to be reading them at the time.

Granted, you're right - it's YC's sandbox and they get to set the rules. But reading dang's post I can't help but wonder whether he's confusing diversion for intellectual quality.