  This research investigates how people engage with data visualizations when
commenting on the social platform Reddit. There has been considerable research
on collaborative sensemaking with visualizations and the personal relation of
people with data. Yet, little is known about how public audiences without
specific expertise and shared incentives openly express their thoughts,
feelings, and insights in response to data visualizations. Motivated by the
extensive social exchange around visualizations in online communities, this
research examines characteristics and motivations of people's reactions to
posts featuring visualizations. Following a Grounded Theory approach, we study
475 reactions from the /r/dataisbeautiful community, identify ten
distinguishable reaction types, and consider their contribution to the
discourse. A follow-up survey with 168 Reddit users clarified their intentions
to react. Our results help understand the role of personal perspectives on data
and inform future interfaces that integrate audience reactions into
visualizations to foster a public discourse about data.
