how to set to write users comments permanent on site

Grzegorz,
Google has publicly stated that they already crawl the Javascript comments from Facebook. There used to be a way to force the comments into the actual HTML, but it's no longer necessary since Google and other search engines know how to 'see' the comments anyways. The method to put the comments into the HTML slows down page load times and overall isn't worth the extra issues it causes since the search engines don't need the comments in the content.

Hope that helps explain,
Alex