Why can't Rosette really use any idioms without mispronouncing/misusing a word? She was a Street Urchin in the Empire (which heavilydiscriminates against non-humans, thanks to theirreligion) in her early years, so there is little chance for her to learn "proper" speech back then, and even after she moved to a more monster-tolerant area and earned all that money by working as a mercenary, given her personality, it's more likely than not that she only learnt those idioms and phrases from overhearing them in someone else's conversation instead of actually learning about them using a dictionary or so. Hell, it's already a miracle that she is literate given her upbringing.
Where did Levan learn to use the repeating crossbow in Volume 4? Remember that he used to go on camping and hunting trips back when he was on Earth. Although the dream sequence is about him being good with the Colt 1911 (which the demon-princesses dredged up from his apartment along with a few rounds), he would most likely be using a rifle or a shotgun when he's actually hunting. The description of the repeating crossbow he used indicated that the weapon have a similar handling with a bolt-action rifle - which is commonly used for, well, hunting.
Why is it that pretty much every time Levan got into a fight he is either forced on the run or got his ass handed to him? Although he is not exactly famed aside from the wanted poster courtesy of the Inquisition, pretty much everyone in the world knows Rosettethe Thorn Knight, and any of Levan's adversaries would be more than likely prepared to fight her upon knowing whom Levan is accompanied with - which would also mean absolute overkill when going against Levan.
1) Where are her parents? Especially that salamanders are both VERY rare and known for their combat prowess, what happened to her family that she had to scavenge for life in some backwater town of the Empire, which is known to be highly xenophobic thanks to the church? Were they once residents in a nearby area and purged by theInquisition?
2) Rosette is a salamander, one with an extraordinary healing factor and the capability to control her body temperature to keep herself alive and healthy. Most other non-human species do not have such powers. Just how many non-human children are forced to live in such horrid conditions and die to diseases?
Most people wouldn't have irrational fear or utter hatred of those they once treated as their siblings, even after a life-threatening accident. Just what the hell was Deron taught about wyverns and dragons? Given that he was a pawn of the church, did the church feed him all those vile Propaganda Pieces against the dragon-kin and Domdracvaria in general in hopes of turning him into a crusader against his former Childhood Friend and even his own sister?
Just why or how would Levan call Shoshanah "Susan"? All other nicknames Rosette gave her during their bickering didn't stick with him, and he managed to pronounce her name correctly before all the bickering started, and that's before the fact that "Hannah" can be considered as a legitimate shortening of her name (shares the latter two consonants and the last syllable, and have a similar spelling) and "Susan" much less so.