Third-party commenting engines like Disqus, Facebook Comments or Intense Debate make it easy for you to enable commenting on any website /blog but there’s one downside – some of these commenting engines are implemented in JavaScript and hence search engines may not be able to read /index the comments that visitors are writing on your web pages.

In other words, your web pages will rarely get any SEO boost as comments are rendered in JavaScript within an <IFRAME> and hence the text is not visible to search engines.

That seems to have changed recently at least in the case of Google. [Update] This was later confirmed by Matt Cutts - “Googlebot keeps getting smarter. Now has the ability to execute AJAX/JavaScript to index some dynamic comments.”

Googlebots, or the spiders that crawl web pages,   are now reading Facebook comments on websites just like any other text content and the more interesting part is that you can also search the text of these comments using regular Google search.

To give you an example, here’s a comment from Robert Scoble that he has previously written on a TechCrunch page using the Facebook comments system..

..and here’s the same comment available through Google web search. You can in fact use search queries like “commenter name * commenter title” (for example – “Robert Scoble * Chief Learning Officer at Rackspace”) to discover all comments that he or she may have written on various websites that use the Facebook comments platform.

If you have so far avoided using Facebook comments on your website /blog just because of the SEO factor, you may want to reconsider your decision now.

However I am not too sure if Google would pass any juice to any of the website links that some people may be dropping in your comments. Also, moderation of Facebook Comments is all the more important now as the comment text is part of the page content itself and you don’t want to be in violation of Google’s Webmaster Guidelines just because of those angry comments that do not use very civilized language.