There is a famous chart that circulates among international managers. In the left column are the things that British speakers say. In the middle are the things they mean. In the right column are the things that foreign listeners understand. "I'll bear it in mind" means "no", but is heard as "yes". "Not bad" means "excellent", and is heard as "mediocre". "With the greatest respect" means that none is being offered, and is heard as respect.
The chart is funny because it is true, and misleading because it suggests that understatement is a national failing. It is nothing of the sort. Every language has its codes. In some, enthusiasm is the default, and a lukewarm reply is a warning. In others, silence is the highest compliment, and a sudden burst of praise is slightly suspect. The problem is not the code but the listener who does not have it.
Understatement works best between people who share a history. A quiet "that was not unpleasant" from a lifelong friend is a medal. The same sentence, said by a stranger, is a puzzle. When the code is shared, indirectness is a form of intimacy: I trust you to complete my meaning. When it is not shared, it becomes a form of defence: I say something, and I may later claim that I said something else.
This is why international teams so often fail without anybody being rude. Each person is behaving perfectly in their own system. The British manager, hearing "this is a challenging idea", concludes that the project is lost. The Dutch manager, hearing "that is quite good", prepares the champagne.
The solution is not to abolish understatement, which would make the English language unbearably loud. It is to carry, when travelling, a small piece of honesty: a sentence that says what you mean, and a second that says what you would like the other person to do. That is not an insult. It is a bridge.
Fiction note: All people, places and events in this text are fictional.