WordPress.org

Why doesn't it work on my theme?

Your theme may substantially deviate from standard WordPress comment section HTML layout. The plugin was developed against the Twenty Ten theme. Try another theme, or try standardizing your theme's HTML. I don't plan to add support for other markup — I'd rather that people work on standardizing their theme comment markup instead.

Doesn't this prevent search engines from seeing comments?

No, it doesn't! Through the magic of Google's "AJAX Crawling" specification, search engines (currently Googlebot and Bingbot) will be made aware that the page includes AJAX-fetched content, and will request your page with a special URL that will have this plugin skip AJAX-generation and instead give the full HTML to the crawler.