  Recent studies, targeting Facebook, showed the tendency of users to interact
with information adhering to their preferred narrative and to ignore dissenting
information. Primarily driven by confirmation bias, users tend to join
polarized clusters where they cooperate to reinforce a like-minded system of
beliefs, thus facilitating fake news and misinformation cascades. To gain a
deeper understanding of these phenomena, in this work we analyze the lexicons
used by the communities of users emerging on Facebook around verified and
unverified contents. We show how the lexical approach provides important
insights about the kind of information processed by the two communities of
users and about their overall sentiment. Furthermore, by focusing on comment
threads, we observe a strong positive correlation between the lexical
convergence of co-commenters and their number of interactions, which in turns
suggests that such a trend could be a proxy for the emergence of collective
identities and polarization in opinion dynamics.
