I would like to explain my rationale, because I have a feeling there will be questions.
In the broadest sense, I tiered the characters by “the impression they left on me.” That is to say, the length of screen time is only a relative factor. If a minor character is a major part of one of my favorite scenes, even if that is the only scene that character is in, then that is weighed heavily in that character’s favor. The result is minor characters interspersed among major ones, and I’m okay with that.
Two characters not included in this tier list that I wanted to include are Henry the Horsefly, who would be in A tier in between Butterscotch and Honey, and Angela Diaz, who would be in A tier between Diane and Herb. I probably think about Angela’s second encounter with Bojack more than any other scene in the entire show.
Obviously, each character’s moral foundation is a complete non-factor in this tier list. You’re not gonna catch me rating Joseph Sugarman low just because he’s insensitive.