As civil discourse increasingly takes place online, misinformation and the\npolarization of news shared in online communities have become ever more\nrelevant concerns with real world harms across our society. Studying online\nnews sharing at scale is challenging due to the massive volume of content which\nis shared by millions of users across thousands of communities. Therefore,\nexisting research has largely focused on specific communities or specific\ninterventions, such as bans. However, understanding the prevalence and spread\nof misinformation and polarization more broadly, across thousands of online\ncommunities, is critical for the development of governance strategies,\ninterventions, and community design. Here, we conduct the largest study of news\nsharing on reddit to date, analyzing more than 550 million links spanning 4\nyears. We use non-partisan news source ratings from Media Bias/Fact Check to\nannotate links to news sources with their political bias and factualness. We\nfind that, compared to left-leaning communities, right-leaning communities have\n105% more variance in the political bias of their news sources, and more links\nto relatively-more biased sources, on average. We observe that reddit users'\nvoting and re-sharing behaviors generally decrease the visibility of extremely\nbiased and low factual content, which receives 20% fewer upvotes and 30% fewer\nexposures from crossposts than more neutral or more factual content. This\nsuggests that reddit is more resilient to low factual content than Twitter. We\nshow that extremely biased and low factual content is very concentrated, with\n99% of such content being shared in only 0.5% of communities, giving credence\nto the recent strategy of community-wide bans and quarantines.\n