I do that too. I had a fic a while back where Draco is reading out some notes from a Doctor, referencing a greek word for the verb 'to obey'. The word actually had pi in it, lol, and I had Remus say the word, while Harry, who couldn't understand the word, said "Eepakooey?" and Remus answers with "Close enough." When I spell out the word as it's said (I just learned from you it's called Cyrillic, so thanks!) readers can follow as if they're characters and not separate from the story.

I understand what you mean by withholding an element of mystery. I do, it's just, as a reader I get frustrated when I don't know what's being said. It piece of dialogue I'd read at the time wasn't part of a mystery. It was a conversation between Draco and Fleur about babies. *shrugs*

If it had been used as a part of a mystery I might have been able to forgive the author, lol.