Disqus comments integration - SEO Benefits or implications
For Non- Drupal /Wordpress sites unless your site taps into the Disqus API and embeds them into your site in plain HTML. Disqus allows for indexing with google but I'm not sure what mechanism they require in order to do so.
Disqus is about active commenting community and SEO is not main goal, it is a nice side effect. Users spend more time on pages where Disqus is installed. This translates into more page views and more comments, which keep pages fresh and give search engines more data to crawl. They work with search engines like Google, to ensure Disqus is crawlable, though ultimately, indexing is out of Disqus’ hands. That being said, there is always the option to sync comments locally to be rendered in the HTML of the page.
WordPress / Drupal plugin of disqus which automatically syncs comments, we're going to use it as the example on how to sync your comments locally, both for backup and SEO. See here: http://docs.disqus.com/help/58/ for info on how to synch and render your Disqus data locally for backup and SEO purposes
Another impact of disqus is that it increases your page load time. APIs can suck up page load time.