morriswalters - I hope I haven't caused you offense. Perhaps we will discuss it further one day. And by "all of the fey" you mean some I think...at that particular battle several characters and creatures were described specifically using other weapons (e.g trolls with clubs, fey with spears, Winter Lady and Queen etc.) But really we are talking about humans, not creatures of magic. Specifically Wizards - who largely rely on magic for combat. My memory of the humans that use swords are (the 4 knights of the cross - butters only technically, Nicodemus himself - I don't recall ANY other Denarians using swords as most rely on their Fallen's monster form, Lloyd Slate and Fix - as Winter and Summer Knight respectively) But most don't (the Denarian squires use guns, Kincaid doesn't use any swords - though he isn't strictly speaking human, none of the cops other than Murphy, None of the Black Court Vampires, only some of the Reds - they also use obsidian axes and blades rather than traditional swords, the White Court Vampires do - but they also use guns and explosives just as much and are considered the most modern of the Vampire Courts, Charity uses hammers, Molly doesn't use swords, none of the priests, not Marcone or his people apart from Gard who is probably a Valkyrie etc.)
Harry likely learned fencing like everyone else does - in a class. Fencing classes are everywhere. But the only teach fencing as a sport, anyone old school (like Morgan or Luccio or Grevane etc.) would have learned it not for sport but for defense. Warden's likely learn it from each other. He has fought twice I believe as he normally likes to express Earth Magic through his sword cane - primarily electromagnetism. He has used the blade though, I will have a search around for the text. But he does it rarely, as like most wizards he relies heavily on magic in combat. Sword users that have been described, especially humans are in the minority in the series. Don't get me wrong, I love sword fights and duels. Great stuff to watch, I have seen many acted out and been to many fencing competitions not to mention watching many online. I have actually seen the JB proposal which was very sweet. But none of this means that Swords are common to humans (especially magic humans) in the series.
Maz - I think you are confusing Harry piercing veils with magic and his powers of deduction. He recognised Talos and Korrick through process of elimination (he knew Auror was behind the theft of power, meaning her people would be the one's with her but he didn't "see through" the veils sphysically. He would have had to use his Sight). I believe in the Mavra case you are referring to is when he first meets her at Bianca's ball. In that case he used his magical "sense" to work out where an invisible person was - but again did not "see" through the veil. He would have had to call upon his Sight. Which he does to Ariana during the duel with her - but any practitioner with the Sight could do such a thing. It is hardly unique to Harry. He is frequently missing veils actually (Cowl and Kumori snuck up on him, Elaine and Korrick catch him straight off guard despite almost being on top of him, Martha Liberty was only feet from him an Ebenezar yet he wasn't even slightly aware of her and Listen's to Wind etc.)
Would you recognise her? Even with a physical disguise that obscured her body shape and face, and a magic voice distorter? Its conjecture anyway. The fact is Harry does not recognise Kumori. We can only speculate as to why. Perhaps he wouldn't recognise Faith or Jenny after so many years even without all the other disguises, but we cannot know this. And likely if Faith, Jenny and Elaine were all in a room with him wearing a simple mask he probably would only recognise Elaine if anyone. Because of how well he knows her. But if Elaine were Kumori, all the more reason to hide every recognisable part of herself. You don't argue the impact of Elaine, but we do have the facts that support Elaine over the other two (including that the reveal of Kumori will hurt Harry alot) and yet as I understand your argument to be it couldn't be Elaine because Harry is hyper-observant. But if Kumori's disguise trumps Harry's observational skills then your only reason that it couldn't be Elaine falls apart. Realistically if you were a detective trying to work out who Kumori was would you pick the person who most fit the facts or pick a person who might fit one or two of the facts? Does it really stretch belief that it was Elaine in front of him the whole time in disguise? It is a common trope. Not to mention, it actually happened already with Elaine in Summer Knight. She was with the villains from the start yet he couldn't see it at all. Harry has a huge blind spot when it comes to women, especially in the earlier books and especially ones who seem vulnerable. It is constantly used against him.
Raidem - Ah yes I remember that theory. It would be an excellent betrayal. However as we don't yet know how time travel works in the series, it is still a bit of a long shot. Remember Vadderung says that it is difficult and extremely dangerous to mess with the past - not to mention the Law of Conservation of History (as Harry calls it - the effect Odin describes is that events in the past tend to happen always the same way as there is a quality similar to inertia at work). However I could see it being regular old Maggie Snr who has transcended her Death.
I haven't yet read the Amber Chronicles - it is on my to-do list - but in Amber is the lady that returns a significant character? And does is her return a major plot point? Does it have a long lasting effect on the main character? Was there a lot of foreshadowing? And same applies to the girlfriend. And by "bad actor" do you mean villain or is that a specific type of being or class that exists in the Amber Chronicles?