how would that work any differently than share flag/report? People share when it confirms their bias, and flag/report when they dislike something.
Let's say identical articles get published in Huffington Post and Breitbart (since most journalism is reposting AP/Reuters/Youtube/Imgur/Twitter with a h/t at the end anyway, its not unbelievable.)
The HP article gets shared by the left-bubble and spreads rapidly. Now if The left-internet catches wind of a controversial Breitbart article, they attack. In left-internet the Breitbart article will perish, the HP, flourish.
Because there are 55 hundred million versions of the same article posted across thousands of sources, there are always variants of each story that exhibit each behavior in each community.