As Expected, LJ is changing how the crossposting works.

This will come as a surprise to no one (and, in fact, a change I stated would solve the problem) - but LJ is modifying the new Twitter / Facebook crossposting system...

Per the news post:

We understand and appreciate your privacy concerns. For this reason, we'll be modifying the comment cross-posting portion of the Facebook and Twitter Connect feature so only comments on public entries (those marked 'Everyone') can be cross-posted. Once we implement this change, it will no longer be possible to cross-post screened comments or comments left on Friends Only entries.

Carry on citizens, show's over.