I think you didn't read the request completely. If you are an author on the site, you have a whole set of author tools. On your stats page, there is a section of site-wide statistics, including the number of people that have added you to their "Favorite Authors" list.
What I am proposing the the converse. Readers can, in their account settings, have Favorite Authors. They can also have authors whose works they never want to see - "Blocked Authors." I am proposing that the authors be able to see both the good and the bad. That is, how many people "really like me" as well as how many people have permanently blocked me.
As far as I know, the count of how many people have declared an author their "favorite" is not visible anywhere to readers. Both numbers would be strictly an author tool.
As far as telling people that they won't like what is posted, what do you think story codes are for? Remember that the original purpose of the codes was to allow people to avoid their "squicks" - the things that turned them off - like rape, pedo, scat, and the like.
It wasn't until much later that story codes became a positive, with people searching for things like "school", "sport", etc.