Perhaps they had links that your blog software filtered out?
Well, I've had spam comments with links. Those didn't get approved. But when anyone posts, they have the option of putting their site in the form. And all of those weird comments include a website. Many of the websites don't work though. And I'm just trying to figure out if this is an SEO scheme they're attempting or something else. In addition, they mostly seem to be centered on one post I wrote on zone focusing. It has five comments. I almost believed they may have been real, but they all have mismatched European names (like Millicent Shreves) and all the IP addresses are in Asia.
EDIT: I see what you're saying now. They wanted to post with comments, but were prohibited from doing so directly by Wordpress and went through the approval process instead using the form. So essentially you're saying yes, it's an SEO scheme.