  Centralized social media platforms are currently experiencing a shift in user
engagement, drawing attention to alternative paradigms like Decentralized
Online Social Networks (DOSNs). The rising popularity of DOSNs finds its root
in the accessibility of open-source software, enabling anyone to create a new
instance (i.e., server) and participate in a decentralized network known as
Fediverse. Despite this growing momentum, there has been a lack of studies
addressing the effect of positive and negative interactions among instances
within DOSNs. This work aims to fill this gap by presenting a preliminary
examination of instances' polarization in DOSNs, focusing on Mastodon -- the
most widely recognized decentralized social media platform, boasting over 10M
users and nearly 20K instances to date. Our results suggest that polarization
in the Fediverse emerges in unique ways, influenced by the desire to foster a
federated environment between instances, also facilitating the isolation of
instances that may pose potential risks to the Fediverse.
