We offer a custom XML import format based on the WXR (WordPress eXtended RSS) schema. This is useful for sites importing comments to Disqus in an unsupported format.

Reminders

All fields are required even if they contain no content.
Only use the <dsq:remote> tag (and its children) if you're using Single Sign-On; otherwise remove it.
If you're manually filling in <wp:comment_author_email> make sure it's unique to each user or else all comments will display the same author name.
Each <item> tag can parent an infinite number of <wp:comment> tags.
There is a minimum character requirement for each comment message, which is 3 characters.

Recommendations

Register a test forum and importing to that forum first to work out any kinks.
Keep individual file sizes <50 MB each.

Example Format

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0"
  xmlns:content="http://purl.org/rss/1.0/modules/content/"
  xmlns:dsq="http://www.disqus.com/"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  xmlns:wp="http://wordpress.org/export/1.0/"
>
  <channel>
    <item>
      <!-- title of article -->
      <title>Foo bar</title>
      <!-- absolute URI to article -->
      <link>http://foo.com/example</link>
      <!-- body of the page or post; use cdata; html allowed (though will be formatted to DISQUS specs) -->
      <content:encoded><![CDATA[Hello world]]></content:encoded>
      <!-- value used within disqus_identifier; usually internal identifier of article -->
      <dsq:thread_identifier>disqus_identifier</dsq:thread_identifier>
      <!-- creation date of thread (article), in GMT. Must be YYYY-MM-DD HH:MM:SS 24-hour format. -->
      <wp:post_date_gmt>2010-09-20 09:13:44</wp:post_date_gmt>
      <!-- open/closed values are acceptable -->
      <wp:comment_status>open</wp:comment_status>
      <wp:comment>
        <!-- sso only; see docs -->
        <dsq:remote>
          <!-- unique internal identifier; username, user id, etc. -->
          <dsq:id>user id</dsq:id>
          <!-- avatar -->
          <dsq:avatar>http://url.to/avatar.png</dsq:avatar>
        </dsq:remote>
        <!-- internal id of comment -->
        <wp:comment_id>65</wp:comment_id>
        <!-- author display name -->
        <wp:comment_author>Foo Bar</wp:comment_author>
        <!-- author email address -->
        <wp:comment_author_email>foo@bar.com</wp:comment_author_email>
        <!-- author url, optional -->
        <wp:comment_author_url>http://www.foo.bar/</wp:comment_author_url>
        <!-- author ip address -->
        <wp:comment_author_IP>93.48.67.119</wp:comment_author_IP>
        <!-- comment datetime, in GMT. Must be YYYY-MM-DD HH:MM:SS 24-hour format. -->
        <wp:comment_date_gmt>2010-09-20 13:19:10</wp:comment_date_gmt>
        <!-- comment body; use cdata; html allowed (though will be formatted to DISQUS specs) -->
        <wp:comment_content><![CDATA[Hello world]]></wp:comment_content>
        <!-- is this comment approved? 0/1 -->
        <wp:comment_approved>1</wp:comment_approved>
        <!-- parent id (match up with wp:comment_id) -->
        <wp:comment_parent>0</wp:comment_parent>
      </wp:comment>
    </item>
  </channel>
</rss>