My mental framework has been: - Curly quotes are a typographic sugar that's easier on the human eye when reading normal, human-language text. It's reasonable f

My mental framework has been: - Curly quotes are a typographic sugar that's easier on the human eye when reading normal, human-language text. It's reasonable for them to be automatically inserted into your typing in something like a word processor, and depending on which language you're writing in, there may be strong orthographic rules about the use of curly braces (or their cognates, like « guillemets », etc). - Straight quotes belong in code by a combination of convention and practicality; unicode characters should be escaped wherever it's practical to do so (for example, if you must use "→" in your code, prefer to do e.g. "\u2192" instead -- it's clearer for future users which exact unicode arrow you were using there).