Here's a breakdown:
It can be rude when:
* It's said sarcastically. The tone of voice makes it clear you're not actually happy for the person and are being passive-aggressive.
* It's used to dismiss someone's feelings. If someone is sharing something exciting or difficult, saying "How nice for you" can feel dismissive and insensitive.
* It's said in a condescending tone. This makes it sound like you're belittling the person's experience or achievement.
It can be neutral or even polite when:
* It's said genuinely. You're genuinely happy for the person and are expressing your positive feelings.
* It's used as a simple acknowledgement. You're acknowledging the information shared, but not necessarily expressing strong emotions.
Here are some examples to illustrate:
Rude:
* "You got a promotion? How nice for you! You're always so lucky." (Sarcastic, dismissive)
* "I just broke my leg. How nice for you." (Condescending, dismissing the seriousness of the situation)
Neutral/Polite:
* "You're going on a trip to Paris? How nice for you! I've always wanted to go." (Genuine excitement)
* "You got a new car? How nice for you." (Simple acknowledgement, not necessarily expressing strong emotions)
Bottom line: While "How nice for you" isn't inherently rude, it can be depending on the situation and how it's said. It's always best to consider your tone and the other person's feelings before using this phrase.