These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Magnificent Bastard: Paine all the way. We have yet to see anything he does not working to his advantage. Umbra is even better at it, though mostly off-screen.
Ship Tease: Plenty to go around for just about any pairing.
Noir/Nocte had lots of hints since the beginning: They mostly got along (when Noir wasn’t helping Paine bully her), Noir developed a lot of respect for her when she completely defeated him, and Nocte admitted she didn’t actually hate him. Not to mention all the bickering. There were several times Noir helped her for no particular reason. She thought of him as noble. They had a heartfelt conversation about friendship and love. They dream about each other a lot: Nocte after Savvy betrayed her for him (though that was out of annoyance), Noir for an unspecified amount of time before (and after?) the beginning of the third book and Nocte couldn’t stop thinking and dreaming about him in the fourth book after she killed him and later even admitted (to herself only) that she’d missed him.
Paine/Nocte isn’t far behind, considering she really wants him as her friend. Even though they were supposed to hate each other, Nocte managed to make him see how useless that hate is. They’ve had a truce ever since and developed mutual respect. Paine helped her many times and while it’s always been because of a deal up until now, he even went so far as to risk his life when he hadn’t needed to. They can understand each other with a look and Nocte has learned to read his poker face. He admitted he doesn’t want to kill her and they more or less agreed to “make use of” each other in the future.
Doctor/Nocte suddenly got lots of hints in the fifth book, thanks to being the only Erisirens on Earth. They trust each other implicitly, even when Doctor has no idea what she’s doing. They always think in terms of “us” and “we”, not “I” and “you”. They learned to understand each other with just a look. She never felt like a Damsel in Distress and never thought she needed a hero until she had a breakdown and Doctor was the one to help her get up again.
Farhat/Nocte: To start with, she’s the only one who can normally see him and talk to him. He’s the only one who can easily get past her mental barriers to read her thoughts. Farhat bent the rules to resurrect someone as a favour to Nocte. When Umbra died, the sight of her crying hurt him and when Nocte later told him to never show himself again, they both ended up crying. Reapers aren’t even supposed to be able to feel. Even though he didn’t show himself for half a year, he kept tabs on Nocte and her friends. He was desperate to keep her alive when she fell into Arctic waters and has since rescued her life several times. And then there was the time when she was completely out of it and almost kissed him.
Darkhour/Nocte: In the first book, they teamed up to dance tango, complete with groping. She’s thought of him as a sort-of friend ever since. They got along so well that a certain shop assistant is convinced they had something going on. He warned her (during another impromptu tango session) that Blackthorn had taken a hit out on her, even though he was supposed to be on Blackthorn’s side. He tried to help her several times.
Bloodstone/Nocte: He seems really interested in everything she does. He finds her amusing and there was a time he actually genuinely laughed because of her. Not to mention the fact that he keeps cranking up the pheromones when she’s around. It’s like he wants to keep trying until it finally works on her.
Aman/Nocte: Aman has been her best friend since before the series started and it shows. They can talk about anything and forgive each other everything. They trust and protect each other no matter what. The other’s safety is always at the forefront of their minds. Aman is also usually the one that talks sense into Nocte whenever necessary.
Mêi Fèng/Nocte: Mêi Fèng owes Nocte everything. Nocte protected her life almost at the expense of her own. She is Mêi Fèng’s main support whenever things get difficult. Nocte has faith in Mêi Fèng and, in turn, Mêi Fèng trusts Nocte more than anyone else. Not only are they very close friends and allies, they also promised to become sworn sisters before the Heavens, so that no one would ever dare try to keep them apart.