When using Disqus 2.74, the link to leave/view comments at the top of a post points at a URL that does not exist, eg:
Note that the same links on lists of posts (eg, home page) do point to working URLs, eg:
This seems like it's an issue in any theme, including standard WP themes like Twenty Twelve.
An example of the rendered link HTML on a post:
<div class="comments-link"> <a href="http://localhost/example-post/#comments" title="Example Post"><span class="dsq-postid" rel="7 http://localhost/?p=7">6 Replies</span></a> </div>