Duplicate articles within a short timeframe, sure. But this is more down to users submitting and/or commenting/upvoting on threads when stories are already submitted earlier. Not reading the site, thinking they're somehow ahead of things. Stuff moves pretty fast. Missed the discussion? Well, there's the link.

HN does detect direct duplicates upon submission (ie same url).

But in instances like this one where it's different articles about the same topic, there's presently no real detection. I'm not sure there should be either, with them being different articles and all.