Better When It Was Smaller? Community Content and Behavior After Massive Growth.

Online communities have a love-hate relationship with membership growth: new members bring fresh perspectives, but old-timers worry that growth interrupts the community’s social dynamic and lowers content quality. To arbitrate these two theories, we analyze over 45 million comments from 10 Reddit subcommunities following an exogenous shock when each subcommunity was added to the default set for all Reddit users. Capitalizing on these natural experiments, we test for changes to the content vote patterns, linguistic patterns, and community network patterns before and after being defaulted. Results support a narrative that the communities remain high-quality and similar to their previous selves even post-growth. There is a temporary dip in upvote scores right after the communities were defaulted, but the communities quickly recover to pre-default or even higher levels. Likewise, complaints about low-quality posts do not rise in frequency after getting defaulted. Strong moderation also helps keep upvotes common and complaint levels low. Communities’ language use does not become more like the rest of Reddit after getting defaulted. However, growth does have some impact on attention: community members cluster their activity around a smaller proportion of posts after the community is defaulted.