HN is my top candidate for a solution like this, too. Because there's a ton of high quality content here, increasingly buried beneath a small number of sentiments and topics I don't care to see rehashed constantly.
replyI'd like to see it, too, but for the opposite[1] reason: Others can use this curation (which only affects their own view of HN) instead of flagging (which affects my view and everyone else's too).
replyI use the flag functionality as per the guidelines:
reply> Off-Topic: Most stories about politics, or crime, or sports, or celebrities, unless they're evidence of some interesting new phenomenon. If they'd cover it on TV news, it's probably off-topic.
> If a story is spam or off-topic, flag it. Don't feed egregious comments by replying; flag them instead. If you flag, please don't also comment that you did.
Flagging is a way to shape what types of content takes up the finite amount of attention available on HN. If everyone used it (only) in the way the guidelines ask you to, the front page would look very different on a given day.