This is wordpress auto-generating a comment in your existing article when you refer to it at a later date. It means your old article is automatically updated with something you discuss on it at some point in the future! (saves you going back and editing something old!)

Is this some weird wordpress behavior where occasionally when you post a new article it also deposits a random snippet of it in the comments of one of your other articles? Or, is it a weird wordpress behavior in response to someone external trying to do some manipulation of your comments?

I think luckily though, the true spammers haven’t quite caught up with the nofollow community.

The worst though is people replying on your blog as a thankyou (for what you said on their blog). Kind of hard to delete the comments, despite it being obvious that they aren’t interested in what you wrote yourself!