I can definitely see how you might need this... yet it one sense, you could think of it as redundant. If you restrict all of author "Vanessa Blaylock's" posts to the "Vanessa's World" category, then that category is self-similar to the Vanessa Author Archive. I guess you could restrict both Sarah & Vanessa to the "smart people who are not men" category... so that could be useful.

In my own case, I run a few multi-author sites where all authors are free to post in any category. The issue I have is that I prefer posts to have 1 category and any number of tags. I always feel that checking 6 different categories isn't helpful because then all the same posts come up regardless of what category archive you look at. I think of categories as overarching theme and tags as any items touched on in the post.

The problem is that when an author looks at the backend they see a blank box for tags, so many of them just leave that blank, and they see all sorts of choices for categories to check off, so they check a bunch. I realize that technically checkboxes for categories and a text box for tags makes sense, yet functionally it seems to often encourage authors to do the opposite of what I had in mind. I've tried explaining this to authors and that often doesn't work. If these were paid authors that message might be easier to transmit, but these are art & culture sites where everyone is freely sharing their projects and ideas and sometimes that degree of communication is hard. I've mostly stopped trying to explain it and I do just "clean up" the categories in the backend manually. It only takes a minute per post, so it's easy.

What I personally wouldn't mind is the option to change categories from Check Boxes, to Radio Buttons. Then authors could choose any category, but they'd be forced to pick the (hopefully) most relevant category and not just click 6 of them.