  Echo chambers in online social networks, whereby users' beliefs are
reinforced by interactions with like-minded peers and insulation from others'
points of view, have been decried as a cause of political polarization. Here,
we investigate their role in the debate around the 2016 US elections on Reddit,
a fundamental platform for the success of Donald Trump. We identify Trump vs
Clinton supporters and reconstruct their political interaction network. We
observe a preference for cross-cutting political interactions between the two
communities rather than within-group interactions, thus contradicting the echo
chamber narrative. Furthermore, these interactions are asymmetrical: Clinton
supporters are particularly eager to answer comments by Trump supporters.
Beside asymmetric heterophily, users show assortative behavior for activity,
and disassortative, asymmetric behavior for popularity. Our findings are tested
against a null model of random interactions, by using two different approaches:
a network rewiring which preserves the activity of nodes, and a logit
regression which takes into account possible confounding factors. Finally, we
explore possible socio-demographic implications. Users show a tendency for
geographical homophily and a small positive correlation between
cross-interactions and voter abstention. Our findings shed light on public
opinion formation on social media, calling for a better understanding of the
social dynamics at play in this context.
