Oh, translation is hugely cultural, maybe entirely cultural. This has bedeviled translators all the way back to when Martin Luther first wrote seriously about translation. You have to recreate the meaning of something that exists only in the source culture, in a language that has no words for it, or that has to express it in an entirely different way.
"Some American reviewer of Foucault’s Pendulum said something nice about the translation, but then said, “I feel that the translator has taken a lot of liberties with the original,” and then he put in parentheses, I’d like to know what the Italian for “couldn’t tell shit from Shinola” was!"
[William Weaver, Umberto Eco's longtime translator]
Another more concrete example from William Weaver.
"Some of the hardest things to translate into English from Italian are not great big words, such as you find in Eco, but perfectly simple things, buon giorno for instance. How to translate that? We don’t say “good day,” except in Australia. It has to be translated “good morning” or “good evening” or “good afternoon” or “hello.” You have to know not only the time of day the scene is taking place, but also in which part of Italy it’s taking place, because in some places they start saying buona sera (“good evening”) at one p.m. The minute they get up from the luncheon table it’s evening for them. So someone could say buona sera, but you can’t translate it as “good evening” because the scene is taking place at three p.m. You need to know the language but, even more, the life of the country."
I can see how there may be no equivalent for a certain idiom, or how social rules can alter the meaning of things, but I don't see how that will lead to a need to dispense with the original meaning of the conversation entirely and just aim for the feel of it.
Maybe I just need to be bedeviled by it myself in the role of a translator to understand.