Hacker News Reader

You can do a similar thing for Google with the uBlackList extension: https://chromewebstore.google.com/detail/ublacklist/pncfbmia...

This should come preconfigured with pinterest and quora blacklisted.

Haha :-)

I always feel bad if I click on any of those sites.

Indeed, but AFAIK you can't do the opposite (make results from certain sites show up higher in the results), which you can do with Kagi.