..."For comments, the Facebook update will say "[Your name] posted a new comment to 'dewhitton' at LiveJournal.", and will contain the subject and text of the comment, as well as a link to the entry. The Twitter update will contain either the subject of the comment or a snippet of the comment itself, as well as a short URL directly to the comment on LiveJournal.
Please note that you can choose to have comments posted to protected entries cross-posted to Facebook and/or Twitter, and the text of those comments will appear to all your followers on those sites, but clicking the link will not show the full entry to anyone who does not have access to view it. The cross-posting options will automatically be unchecked when commenting to a Friends Only or Private post, so that no protected comments are sent to Facebook or Twitter by accident."
It's still a dumb idea. Facebook will fill up with even more inane, empty posts of "I posted a comment to an entry." It's bad enough when everyone announces to the world their cow in Farmville had a crap.
Dreamwidth, Blogger and Live Journal are for writing journals, Facebook is for notes, and Twitter is for -- let's be honest, here -- brain farts. I don't see a need to mix them together.