Awesome Ego: Layla. It sometimes feels like half her dialogue consists of her boasting about how awesome she is. No one's complaining, though.
Badass Decay: Queen Quintessa is initially a huge threat, yet Nina and Tia invade her subconscious right under her nose, and she's assimilated back into Layla's mind with little fanfare.
Base-Breaking Character: Really, you won't find many characters who haven't alienated some fans, at some point.
Nina is also extremely polarizing. She's either loved for her naivety and willingness to openly show affection (in contrast to Layla's Tsundere personality), or she's loathed for how childish and annoying she is. Made moreso, since it was usually either her sister or Ace, who suffer from her actions.
Tiffany is either a cute Plucky Girl whose epic fails to kill a monster are always good for a laugh, or a one-note side character who is even more annoying than Nina.
Ace is rather divisive. While some readers see him as a nice guy who has to put with Nina's antics and empathize with his constant state of misery and self-loathing, others find him to be too normal compared to his wacky friends and detest him for his conspicuous lack of a backbone.
Some fans love Tia's cute design and her ability to stir up drama and tensions in Volume 3, while others believe that she is a completely unenjoyable character and consider her a completely unnecessary addition to the comic.
Blair is quite possibly the most controversial character of the series. His unique take as a hammy Panty Thief split the fandom over those who found it hilarious and those who thought he was the most annoying gimmick in the series and just wanted him gone. Then there's the fact he's a Dirty Old Man in the body of a doll who likes harrassing girls, which put a lot of people off.
The Hellrune Coven were added to the list of characters that got a pinup if you ordered the print edition of Vol.0, and became popular enough to be given their own Spin-Off series: Magick Chicks.
Tiffany's fans loved her for being a Large Ham and a ditz, and because of what they perceived as an attraction between her and Layla. So she was given a bigger role in Magick Chicks, where she became a main character.
Fan Nickname: A large portion of the fandom insists on using the name "Grace" for Ace since he became a girl, even though he's never been called that in strip, or even been addressed with female pronouns.
The first was when Ace was asked to deliver a note to Kade and simply told him to read it, but forgot to mention it was from Nina; so Kade assumed it was from him.
Dio's ongoing relationship with Ash came about as a result of a blastfrom Mel's wand. Which caused some minor contention among the fans, since both characters had been heterosexual, until that moment, and the effect has yet to be reversed.
Female example: Since some of the characters are bi/bi-curious, there's been a decent amount of girl-on-girlfanservice.
Brooke secretly nurses a one-sided crush on Layla and was given a Practice Kiss by her, after asking Layla to show her how, in return for giving Layla some of her blood. Though now that Layla's regained her memories as Queen Quintessa, she's shown up in Ace's dream, along with a past incarnation of Brooke, and says she belongs to her.
Hollywood Homely: Ace is often described as ugly and is frequently insulted over his "furry hands", despite being drawn as attractive as any other character.
Moe: Supposedly, Chloe's entire family consists of more traditional Sexy Devil-types (though we've yet to see them), and she feels ashamed that she can't live up to traditional Succubi standards. Of course, as it is pointed out, she is appealing directly to a much...different aesthetic. Let us count the ways: she's clumsy, wears glasses, manages to attract male attention without really meaning or wanting to, and, of course, she has ridiculously large breasts.
Dio and Kade lying to Ace about his girl-persona, Acina taking over his body during full moons, just so they can continue having sex with her. Seen in thefollowingposts and the rest of the thread.
Blair. A large number of fans have a serious dislike for him, some even going so far as to avoid reading chapters in which he plays a prominent role, or even dropping the series because of his existence. The reason generally stems from the fact he's a Dirty Old Man and a Panty Thief. Despite his genuine concern for Layla and Nina, he mostly groped and harrassed every female in sight. So the readers and the cast themselves were glad to finally be rid of him when when Tia took him away in the final chapter.
Kade and Dio both became universally despised by the readers, due to their actions in the aforementioned story (note under Never Live It Down), leaving Ace and Ash as the only legitimately nice guys in the comic.
.