Ancient echo chambers

Echo and Narcissus, British Library, Harley MS 4431, f, 134r (c. 1410 AD)

The good thing about social media, they say, is that it promotes dialogue and exchange. And there's no better way to test views and ideas than through disputation and scrutiny. Except that social media, as you're surely aware, doesn't really do that. Instead, it sets up bastions of…