Clarified comment about Disqus shortname

Author: barryclark

_config.yml

@@ -30,7 +30,8 @@ footer-links:
   stackoverflow: # your stackoverflow profile, e.g. "users/50476/bart-kiers"
   youtube: # channel/<your_long_string> or user/<user-name>
 
-# Your disqus shortname, entering this will enable commenting on posts
+# Enter your Disqus shortname (not your username) to enable commenting on posts
+# You can find your shortname on the Settings page of your Disqus account
 disqus: 
 
 # Enter your Google Analytics web tracking code (e.g. UA-2110908-2) to activate tracking