Originally Posted by solars

Are you sure you did not mix up comments and trackback links?

yeah its actually a wordpress feature, the code that executes the pings is in wp-admin/execute_pings.php
trackbacks need an entry in post.to_ping (newline separated urls), rpc pings need an entry in post_meta.

I did not go through the whole code but I guess it just sends the trackbacks, wether or not the receiver can handle it.
I'm using lyceum but I think thats default wordpress functionality