CDATA close tag being replaced

Hello,

why is WordPress replacing the CDATA closing tag?

It’s inside wp-includes\post-template.php:167:
$content = str_replace(']]>', ']]>', $content);

http://adambrown.info/p/wp_hooks/hook/the_content?version=2.8&file=wp-includes/post-template.php

What’s the reason for it? Please answer. I see a lot of people asking about it here: http://ww.wp.xz.cn/tags/cdata

Thanks,
M.