Apparently
anyone can add one or more
trackbacks when they make a post in a thread.
That trackback is then listed as "Already Pinged" for ever after - presumably to avoid duplication of effort - and is visible to everyone else that replies to the topic.
The trackback remains even if the associated post is deleted.
So a spammer pops in, creates a trackback and you all get to see it. There's nothing that can be done, but then nothing to worry about either - your system is neither responsible nor affected.
And yes, I have alerted the admins and suggested to them that trackbacks be disabled.
SD