  Increasingly people form opinions based on information they consume on online
social media. As a result, it is crucial to understand what type of content
attracts people's attention on social media and drive discussions. In this
paper we focus on online discussions. Can we predict which comments and what
content gets the highest attention in an online discussion? How does this
content differ from community to community? To accomplish this, we undertake a
unique study of Reddit involving a large sample comments from 11 popular
subreddits with different properties. We introduce a large number of sentiment,
relevance, content analysis features including some novel features customized
to reddit. Through a comparative analysis of the chosen subreddits, we show
that our models are correctly able to retrieve top replies under a post with
great precision. In addition, we explain our findings with a detailed analysis
of what distinguishes high scoring posts in different communities that differ
along the dimensions of the specificity of topic and style, audience and level
of moderation.
