Personally, I only use italicization when I make a digressive sidepoint (for instance, using e.g. or examples given), or offer a different perspective away from the central voice I use. Its a matter of formatting preference though. Italicization helps improve readability of writing if used correctly
I have never really seen anyone in the states use italicization with the "No, thank you" example. Its better to just use emojis instead to get the same message across. Italicization used this way is sometimes treated as sarcasm or passive aggressiveness. Using italicization this way more excessively eventually goes to things like * <bashes away at keyboard> * or writing actions in written form. Those aren't subtle, but they are really awkward to read.
I have never really seen anyone in the states use italicization with the "No, thank you" example. Its better to just use emojis instead to get the same message across. Italicization used this way is sometimes treated as sarcasm or passive aggressiveness. Using italicization this way more excessively eventually goes to things like * <bashes away at keyboard> * or writing actions in written form. Those aren't subtle, but they are really awkward to read.