The change in the point system from 2 type of point (each for Kenna and Dom) to one (apply for all playable characters) in the third game. Its either seen as a chance for more viewpoint characters to contribute meaningfully to the story and more streamlined gameplay or a needless change that reduce replayability. Fans of Dom are particularly unpleased since the new point system is more influenced by Kenna's actions than his compared to the first two games, and vice versa.
Jackson being Promoted to Love Interest. Since Dom was hinted to also be bisexual and that he would have a male romantic interest, many of the fans wondered who would be. Suddenly in Book 3 Chapter 14, it was Jackson who propositioned Dom and got to be a Premium Choice. Some of the fans are accepting of this because it was unexpected and provides more characterization for Jackson, and others didn't so much because of the lack of build up and previous interactions between them. And also there's a portion of fans (mostly female) who think that Dom should be strictly straight.
The mechawolf pup from Book 3, even compared to the other animal party members. Most likely for its hilarious dialogue thanks to Whitlock's technology.
Growing the Beard: While The Freshman is considered to be Pixelberry having a stubble over their last products, Most Wanted and The Crown And The Flame are the books that proved to the audience the company can write a novel that isn't focused on romance and having solid ongoing plots.
Who is better for Kenna? Dom, Raydan, Annelyse, Val, Diavolos or Tevan?
Dom should end up with Kenna, Rose or Sei?
Raydan has received Ship Tease with Kenna, Aurynn and Azura.
Ship Mates: Kenna/Val and Dom/Sei are the most popular ships to those who don't pair Kenna and Dom together.
They Wasted a Perfectly Good Character: Trystan, Rose and Marco (if the player decided to spare him) completely disappear after book 1 despite being major supporting characters in Dom's storyline. The first two didn't even get to interact with Kenna at all, not even mentioning how Trystan never faced any punishment for his betrayal, should Dom not have forgiven him.