I will probably have to update the guide to accommodate for the new QA rules. You can find them here
Now as far as likable characters go... I probably should also update teh definition. But for now, few (if any) trials at the moment star a magnificent bastard villain as the main character you play as. But what I mean by likeable is the kind of character you can learn to like immediately or, with enough exposition, learn to eventually like/sympathize.
The kind of character that never goes well as a main character is the kind that are obnoxiously arrogant and a jerk without a very good explanation. And this is very important in the first case (if for a series), for it's giving the audience a first impression of the character. Remember, first impressions are hard to change. If the character turns off a lot of people, the case and series is doomed from the start. If you want to have a rather unlikeable character as a main character, then it'll take a stronger exposition to hook the players than if the character was likeable from the start.
Interesting note on your opinion on really unlikable people. To each their own... This guide plays on the observations to the majority.
Interesting character, yes perhaps. That might go in a separate definition altogether.