Because writing changes the way you read forever, and I finished Sing the Four Quarters by Tanya Huff and don't feel like a review -- and because aesthetics is still a branch of philosophy. . . .
The profanity was deftly done. Which I noticed because it's so rare. Using modern profanity jars because we all know that profanity is slang and slang changes, so it marks the language as "now" so clearly. (Nevermind that many such terms have lengthy histories. Facts have no chance when you can't suspend disbelief.) And invented ones tend to come across as blatantly fake.
But in the religion of the Circle, you curse things by saying "Center it" or describing it as "unenclosed" -- the equivalent of "damned." It goes down smoothly.
Though some of the other language did not go down as smoothly. At one point, I thought a man describing how his plan would work sounded like an advertising agent. Too jargon-like.
The kigh -- the elemental spirits -- were, unfortunately, given a dichotomy. Here are the Bad Guys who think they are evil, and here are the Good Guys who think they are good and use them in magic. We never, in fact, see them do anything except for the benefit of the Good Guys, usually because their bards are Singing them. Although we are told once that a little girl accidentally burned down her house and killed herself Singing fire kigh. But it strikes me as implausible that they would not act on their own, or that all their actions would be so invariably beneficent. Floods, droughts, windstorms, etc would be much more logical.
It would also let people have many more attitudes toward them. Wary, mistrustful, regarding as dangerous but useful, etc. More plausible than one side or the other. Also, it would have made the Bad Guys' black hats a little less conspicuous.
The broad minded view of the religion has a few holes. If you say that the Circle includes everything, you have to concede that it includes the people who think it doesn't include everything and are willing to kill you over it. You need to have a slightly finer sieve.
I'm not sure that their marriage customs would really work. Agricultural, pre-industrial society -- still a lot of worry about keeping the population up there, and for good reason. You had to have a lot of kids. And these customs are not designed with an eye toward fertility.