Ask HN: Why do certain articles keep popping up from time to time?

I am new to here, so I don't know if this is intentional. But 'Pitchforks are coming' and many others keep on popping up in 'new' category. Why can't mods simply not allow same link to be posted twice?

Also 'Men are likely to shock [..]' is shared many times over. This I think violates HN policy to post the source link. Why not simply post the research paper?