There seems to be a relatively constant stream of posts which outright ask, or include in the text a question about the legitimacy and reliability of the author they're. Currently reading/planning to read. Often the answers are succinct but good critiques of said authors. So how about a sidebar link of author reviews with a grading system based on user input, with user sourced reviews (perhaps flaired users could have higher voting weight also) to help those of us looking to learn?
We actually already have a section on "Historians' Views of Other Historians" in the "Popular Questions" tab located in the sidebar. The links there cover just about every historian that gets brought up on a consistent basis.
As for a grading system for specific authors, I'm not too sure that would be very effective or very representative of any author's body of works. Sure, it may work for an author with one publication, but what about authors who have published several books of varying quality? David McCullough, for instance, has written many popular history books, a lot of them very superficial, but also several pretty good books as well.
In general, I'm also wary about leaving things up to user input on this sub-reddit (even among flaired users), especially concerning the reputability of certain books or authors. Even in a sub-reddit like this which holds very high standards for participation, it's way too common for popular books or theories to be peddled over those that are more historically accurate.
Something to note: despite the constant stream of posts those questions rarely if ever get answered outside of real hotbutton authors like the ones on the wiki or a few pop history writers.
This sort of question is also what the saturday stickied posts are sort of for.