Dialogue is a key component of the vast majority of fiction, and certainly of the kind of books that I read and write. While readers and writers can have distinctively different views on dialogue, often what readers, and even some editors, think is “realistic” dialogue is nothing of the sort.
Over the years a small number of readers have occasionally complained that my dialogue is too formal. And compared to the way many people talk today, it probably is, but throughout history, the educated and professional classes in any society have used more formal dialogue. Some languages even had “high” and “low” versions. Ideally, dialogue should be specific to the characters and their culture, not to what’s comfortable or familiar to editors, but in writing there has to be compromise. I’m not about to write in the equivalent of high German, but the word choice of those who would be speaking in that fashion should suggest formality.
What many Americans, in particular, fail to understand is that most cultures have far tighter social customs and restrictions, as did an earlier United States, than the U.S. does at present. The January 6th attempted “insurrection” at the U.S. Capitol reflects this. In no earlier U.S. period would that many Americans ever thought it proper to storm the Capitol. It wasn’t “the way” things were done. And certain phrases and terms just weren’t used in “polite society.” What tends to be forgotten is that in most societies and times, the equivalent of “polite society” is where the power lies.
In practice, that means less formal dialogue belongs to the outsiders, not the insiders. It also means, even in fantasy and science fiction cultures, if they’re to be realistic, that there should be unlegislated or customary restrictions on what is proper to be said in public, and in private, and on what actions are “beyond the pale.” Obviously, customs change over time in any culture, but history has shown that societies without unspoken restrictions seldom endure, while enduring societies have more unspoken restrictive customs and speech patterns than are obvious to the casual or careless observer.