Here's the thing top comments show up different for everyone. I have multiple YouTube accounts and when I logged in different accounts or when I am not logged in at all. Top comment is based on Google plus following so if you actually use Google plus the top comments will be people in your circles. I think YouTube made a blog post about somewhere. But basiclly if you use Google + you are more likely to be top comment. There is a forum on yttalk where someone proves this also I just don't know the link.
