Would it be
feasible to include an og:image tag on pages for which we have
a reasonable guess as to the thumbnail? Open Graph[3] is supported by what
seems anecdotally to me to be a wide range of services, so good hints there
would improve thumbnails for links on not just reddit, but Facebook,
Twitter, various chat clients, I think several Wordpress plugins, etc.
https://phabricator.wikimedia.org/T33338