It's not the same as bad, either. It means users are engaged with the site and want to share their ideas, projects and experiences on a regular basis. It should be encouraged. Not killed because it might make the site superficially too much like Reddit.
When `dang made his post, my thought was that the activity was harmless and made trying to game Show HN less likely. Thinking about if two weeks later I realize how lame that is as an argument for keeping it.
For better or worse HN is run to meet YC's objectives. YC does not appear to value engagement for the sake of engagement very highly. People can disagree with that, But it remains a fact.
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.
I too argued "It's not that bad" as a reason for keeping it two weeks ago. On the other hand I was not arguing with you at all today since we are in agreement that it's YC's football and it would be absurd to assume that you would argue that I don't hold the beliefs that I had asserted that I hold.
My opinion regarding what beliefs`dang holds is that the 'Idea Sunday' was consistently earning karma disproportionately to it's contribution to the quality of HN and that this was creating a genre of similar high reward high noise threads [e.g. Screenshot Saturday, Tweet Tuesday etc].
My guess is that he looked at the threads closely before pulling the plug, not only because his post implies it but because it was allowed to run for several weeks before he stepped in and moderated. By the time action was taken a fairly detailed picture of who was looking at and participating in the threads was available.
Is it the call I would have made? I don't know because I'm not charged with that, (though I did flag this thread because of its poor quality) and I haven't seen all the facts.