I can not properly display pingbacks

Hello everyone, on the portal where I’m working, there are some post that send a pingback message (link: http://otranto.inonda.le.it/?p=1556) to one post (link: http://otranto.inonda.le.it/?p=1286), but into comments sections appears only the pingbacks number and not the content and / or the origin link.
how to bring up everything?
thanks