Do you know where I should look if I want to moderate all posts where "WAREZ" is part of the message text? Is it ControllerPublic, or the DataWriter? It should be as non-specific as possible, so that everything else works like putting the post to the moderation queue. Here is a screenshot from ZEND searching for "moderate" within xenforos files:
You could extend XenForo_Model_Post::getPostInsertMessageState, but you don't have access to the message text there. Otherwise you can extend XenForo_ControllerPublic_Thread::actionAddReply which saves the actual post.