  This is the first work investigating community structure and interaction
dynamics through the lens of quotes in online discussion forums. We examine
four forums of different size, language, and topic. Quote usage, which is
surprisingly consistent over time and users, appears to have an important role
in aiding intra-thread navigation, and uncovers a hidden "social" structure in
communities otherwise lacking all trappings (from friends and followers to
reputations) of today's social networks.
