Whenever I try to rate my mentor it says:

You cannot rate a mentor at this time.

now 100 trillion credit question... WHY? :)

You can only rate after you've gone up a level.

also, there's no way to find out who rated you poor or good. there's no way to list out your existing students, your past history of mentoring and so on.

"also, there's no way to find out who rated you poor"

That's intentional. If a nOOb rates you bad and you know it, that puts their health at risk.