No guarantees on functionality here, editing from a browser.

app/models/user.rb

@@ -339,6 +339,9 @@ class User
 
   def accept_invitation!(opts = {})
     if self.invited?
+      log_string = "event=invitation_accepted username=#{opts[username]} "
+      log_string << "inviter=#{invitations_to_me.first.from.diaspora_handle}" if invitations_to_me.first
+      Rails.logger.info log_string
       self.setup(opts)
 
       self.invitation_token = nil