If you are having a hard time getting visitors to leave comments, read this article by Problogger Darren Rowse that explains how you can gently encourage and engage your readers, and build a reputable online presence.
Website Grader measures your site’s marketing effectiveness. It gives you a score that incorporates information from Alexa, PageRank, Technorati, Del.icio.us, and offers information about the health of your site (how many links in, from where, etc). Good for an overview, but will never replace a professional SEO audit. Read Michael Gray’s post Why Website Grader is a Bad Idea for more information.