Exploring trackback... Steven, I hope you won't mind me tracking back to your "ping pong" article.
This explains the Trackback mechanism well, I think. Looks like a cool way of building discussion groups on the fly. Time will tell...

Note that that re-editing the entry later on caused pings to be sent again to the linked articles, which makes my trackbacks appear twice there. Sorry folks, I have now switched MT trackback auto-discovery off, hopefully this will not happen again.