instead of using a bot to determine what gets deleted - why not actually look at the posts? the ones being deleted should not have been deleted... after all, you are paid for what you delete, right? should take the time to make sure it is correct and not just some flawed bot logic.
He literally said the script finds possible low value posts and he then manually checks them. FWIW I deleted lots of "thankyou" from newbies and don't see rank or type of signature making any difference.