Lately, I must log out of Google for it to work. Once logged out it does a great job.

You have to go to Extensions and edit the preferences for this -- it does NOT show up in your browser. But it works! I was able to block all Sports news! YES! Sports suck!

Really wish this could block whole sections...

But anyway I found that if you use certain websites that cater to specific types of stories, it will catch more items unambiguously (ex: "sports" might block "e-Sports", but "espn" or "yahoo sports" would block the more traditional kinds). You can also block "more sports" for the section header.

Works fine on my computers, but it doesn't seems to work on Firefox Mobile, sadly.