I have a feeling you can't post on the report itself, but back on the main blog you should be able to at the bottom of the post headed 'Read on!'
I tried to post a reply on the "Read on" page, but it didn't work. After writing the comment and trying to preview it, a new window opened, saying "You need to sign in to wordpress.com to complete this process."
But after opening wordpress and signing in, the window with my comment had disappeared. I seem to have that same problem with other blogs as well, don't know what I'm doing wrong...