approving the publishing of a comment

I have checked “an administrator must always approve the comment”. I find that that is true for a subscriber and a contributor, but here is the strange thing:
An author can approve, edit, delete comments from contributors, authors, and editors but not comments from the highest and lowest levels (subscriber and adminstrator)that does not make sense to me.
Here is my question: how can I prevent an author from managing contributors and editors comments?
Many thanks for your help