Firstly, congratulation on resisting the urge to entitle the post "Karma Police" Secondly, consider one mechanism for why stories might get more likes: do they

Firstly, congratulation on resisting the urge to entitle the post "Karma Police" Secondly, consider one mechanism for why stories might get more likes: do they linger for longer on the home page? If HN population is increasing, then getting to the front page might increase the momentum more now than it used to. And then it collects more likes once it is there.