I believe the code has to be the very first thing in the thread if it is to have any effect.
Anyway, that is according to a note I copied from a post Alex made about it a few years ago.
There is a post from Alex somewhere in the archives that tells exactly how to do and what it protects. I'll try to find it and put up the link to it.
Found it. Here you go.
http://www.ablemuse.com/erato/faq.php?faq=vb3_reading_posting#faq_block_google
and here are all the BBcode lists.
http://www.ablemuse.com/erato/misc.php?do=bbcode#l