where SHORTNAME - this is your site Short Name in SolidOpinion. You may find it in the site settings General tab.
THREAD_URL - you page url without domain.
If you are using SolidOpinion plugin for your site, it will put the link on every page automatically.
<a href="http://api.solidopinion.com/seo/shortname/2/5/thread_url.htmlseo.html">Comments archive</a>
For example for site with shortname example and with http://help.solidopinion.com/knowledgebase/articles/406512 URL, this link will looks like:
<a href="http://api.solidopinion.com/seo/example/knowledgebase/articles/406512">Comments archive</a>How to check whether your link working:
When you'll follow this link, you'll see the plain text of your comments.