The problem with moderation on HN (and other sites) is that all you have to do to be upmodded is to assert something firmly enough. It doesn't have to be even remotely true; people will mod it up regardless. Annoying as hell, and potentially destructive to public discourse when it's as blatantly wrong as the grandparent's post was.
I think comments are good for adding perspective. You shouldn't expect an expert to arrive and give a concise, absolutely true and exhaustive explanation with that perspective. Spurring a community to dig deeper on something previously assumed true is a good thing, right?
The article cited does not claim we've improved cancer treatments - only that mortality from cancer for certain age groups has decreased according to their analysis, which could be from a number of reasons. To my knowledge, one of those reasons is not that a variety of prevalent cancers has been cured to any substantial degree. Also, just because you can find a published article that claims something doesn't mean it's true (although it is a much better chance in the scientific literature versus popular press due to peer review). Especially in an active area like cancer with 10k+ papers, you can basically find a paper that will support any viewpoint.
The NYT is running a great series on cancer treatment that gets into these matters, I should have cited before, here's one of them:
The problem with moderation on HN (and other sites) is that all you have to do to be upmodded is to assert something firmly enough. It doesn't have to be even remotely true; people will mod it up regardless. Annoying as hell, and potentially destructive to public discourse when it's as blatantly wrong as the grandparent's post was.