Pretty simple: there aren’t any. If you find something interesting and want to discuss it, then share it on your favorite social network, and your friends will see what you think.
Unless you have exceptionally boring and stubborn friends, this will stimulate the discussion far better than a random comment on a random blog will.
And if you want to get in touch with me to discuss, peek over to your right (or below, if you’re reading this on a mobile device), and find me on one of the social networks you see there.
Hat tip to my former colleague Kriss Andsten, who inspired this page.