In terms of your specific query, I’m betting that you’re talking about postings on your site like this:
IP Address: 22.214.171.124
Name: Johnny Lee
Email Address: firstname.lastname@example.org
I stumbled on this from Google and wanted to say hello!
I was puzzled by this too, I have to admit, until I did a bit of research and found a very plausible theory on the Movable Type discussion boards: these spam messages are really an advanced party, as it were, they’re creating inbound links to an as-yet non-existent site, with the thought that their comments are less likely to be removed if they’re not pointing to something offensive. Wait a few weeks, build up some inbound links on Google, and then when they do actually launch a site, blammo! Lots of inbound links!
Needless to say, just like any off-topic comments, I think it’s in your best interest to delete these and try to keep some sense of editorial integrity on your Web site. After all, it’s ultimately your name on the top of the page.