Rare, but valuable: Understanding data-centered talk in news website comment sections

News websites can facilitate global discussions about civic issues, but the financial cost and burden of moderating these forums has forced many to disable their commenting systems. In this paper, we consider the role that data visualizations play in grounding discussion around a civic issue, through an analysis of how people talk about climate change data in the comment threads at three news websites (i.e., Breitbart news, the Guardian, the New York Times). We find that out of 6,525 comments, only 2.4% reference data visualizations in the articles. While rare, the paper presents illustrative examples of how people refer to data---their collection, analysis, and visual representation---to engage with an article's narrative. A text classification analysis demonstrates how we might automatically highlight data-centered talk and use data as building blocks for more effective online discussion.