I'm in a similar boat with the "Google Now" feed on Android. When I say "not interested", it fails to note that as expected, and I see the same news "story" pop up (usually different sites, but occasionally the exact same site!). It's likely related to the fact that it almost NEVER gets the subject/topic correct, so I can never use that option.

There was a time I thought I'd trained it to stop telling me about what celebrity said or wore what, but those are creeping back into my feed.