The Agonist has an Internal Message system, letting members communicate privately within the site. Unfortunately, there are problems with it, probably tracing back to the the conversion from Drupal to WordPress. For some people it works, for others it does not work.
Unfortunately, we lack the resources to correct this problem anytime soon.
I am lucky that messages to me do get through, but when I try to send to others, they may be unable to read the messages or get only part of the message. In such cases I would normally send an email, but sometimes our email-of-record for a user is obsolete, leaving us no way to communicate privately.
If the email address you provided when you registered on The Agonist is not current and you are trying to communicate with us privately and unable to do so via Internal Messages, I strongly suggest you use the Contact Page to provide us with a current email address and we will update your user record with the current data and communicate by email.