  Many have criticized the centralized and unaccountable governance of
prominent online social platforms, leading to renewed interest in platform
governance that incorporates multiple centers of power. Decentralization of
power can arise horizontally, through parallel communities, each with local
administration, and vertically, through multiple hierarchies of overlapping
jurisdiction. Drawing from literature on federalism and polycentricity in
analogous offline institutions, we scrutinize the landscape of existing
platforms through the lens of multi-level governance. Our analysis describes
how online platforms incorporate varying forms and degrees of decentralized
governance. In particular, we propose a framework that characterizes the
general design space and the various ways that middle levels of governance vary
in how they can interact with a centralized governance system above and end
users below. This focus provides a starting point for new lines of inquiry
between platform- and community-governance scholarship. By engaging themes of
decentralization, hierarchy, power, and responsibility, while discussing
concrete examples, we connect designers and theorists of online spaces.
