No, I feel the buffet should serve different food to give variety. Those who don't want to dress up can eat there & skip the formal MDR if they choose. Cunard is the only line overall that enforces the dress code across the entire ship.It's comments such as this that cause all the arguments.
As long as Princess allows people to eat in their DR dressed neatly, no one should be taking it upon themselves to be the dress police. True formal dress is not an absolute requirement.
You should re-read Princess's guidelines about examples on to dress dressing on formal nights and you might change your mind.
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