Consider three sentences which could carry very different meanings:
Polite decline: "No, thank you."
Firm decline: "No, thank you."
Scolding decline: "No, thank you."
Perhaps not the best examples, but if italics helps reduce ambiguity and preserve more subtlety, I'm for it.
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.
If I can just ignore them it seems to read better but it's hard work to do so, but maybe that's just me :)