Your Demo

I assume you mean a post like this one? The post length indicator displays the percentage of the page that exists above the #comments div and in the case of that page, about half of the page actually does sit above that div (the comments section starts with the ‘leave a reply’ title).

It’s not the best example site because I don’t get hundreds of comments, which is what this plugin is useful for, but you get the idea from it 🙂