OK some more searching led me to this which helped make it a bit clearer for me.
"Apologies if I presumed too much knowledge in my posts. If you are using a blogging application, like WordPress, there is a facility called Trackback, whereby, when you are making a post in your blog, and you refer to a post someone else made in their blog, you can add in the trackback uri of their post (normally displayed at the end of their post) to your blogging software and it will send a notification (called a trackback) to them.
When their blogging software receives this notification (Trackback), it displays the relevant part of the post in the comments section of the site - as my trackback (no. 67 above) is displayed.
Spammers post faked trackbacks directly to the blogging software, pretending someone has posted about one of your posts, hoping your blogging software will automatically display their spam on your site (thinking it is a legitimate comment).
I hope this clarifies the situation for you - I will post this on my blog, as well as here, and if you require further clarification, feel free to contact me.