Reverted commit 514e848 (issue #236), should fix Disqus identifier issues.

See also: https://github.com/imathis/octopress/wiki/Disqus-identifier-issues

.themes/classic/source/_includes/disqus.html

@@ -5,8 +5,8 @@
       {% if page.comments == true %}
         {% comment %} `page.comments` can be only be set to true on pages/posts, so we embed the comments here. {% endcomment %}
         // var disqus_developer = 1;
-        var disqus_identifier = '{{ canonical }}';
-        var disqus_url = '{{ canonical }}';
+        var disqus_identifier = '{{ site.url }}{{ page.url }}';
+        var disqus_url = '{{ site.url }}{{ page.url }}';
         var disqus_script = 'embed.js';
       {% else %}
         {% comment %} As `page.comments` is empty, we must be on the index page. {% endcomment %}