  We present a method for mapping Reddit communities that accounts for temporal
shifts, using quantitative and qualitative analyses of clustering techniques to
produce high-quality, stable, and meaningful maps for researchers, journalists
and casual Reddit users. Building on previous work using community embeddings,
we find that only a month of Reddit comments suffices to create snapshot
embeddings that maintain quality while supporting insight into changes in
Reddit communities over time. Comparing different clusterings of community
embeddings with quantitative measures of quality and temporal stability, we
describe properties of the models and what they tell us about the underlying
Reddit data. Moreover, qualitative analysis of the resulting clusters
illuminate which properties of clusterings are useful for analysis of Reddit
communities. Although clusterings of subreddits have been used in many earlier
works, we believe this is the first study to qualitatively analyze how these
clusterings are perceived by social media researchers at a Reddit-wide scale.
  Finally, we demonstrate how the temporal snapshots might be used in
exploratory study. We are able to identify particularly stable communities
during 2021-2022, such as the Reddit Public Access Network, as well as emerging
communities, like one focused on NFT trading. This work informed the
development of a webtool for exploring Reddit now available to the public at
RedditMap.social.
