Yes, translation matters. And translation errors can have global consequences. The exact translation of Article 9 of the Japanese Constitution is at issue, since the English version does not say what the Japanese version says. This article is the one in which Japan renounces war, but exactly how and for what period of time depends on which version you look at.
Since the Americans wrote Japan’s Constitution in the wake of World War II, the English version should carry weight, but the Japanese version is considered the source document, the original. Therefore, what it says is what ultimately matters to the Japanese, and the difference in what the English translation says may come as a surprise to many people.
The Japanese Constitution is famous amongst Japanese translators and linguists because it's such a peculiar document. It was clearly written first in English by MacArthur and the U.S. Occupation Authority after the end of WWII and then translated into Japanese. So it sounds very strange in Japanese, very unnatural, very un-Japanese.
But on to Article 9. The important phrase in English is:
In order to accomplish the aim of the preceeding paragraph [to forever renounce war], land, sea, and air forces, as well as other war potential, will never be maintained".
The Japanese text doesn't actually say this. Instead, it says "...shall not be maintained" or "...will not be maintained".
The Japanese text does not anywhere in this phrase have the word "never" in any form, written expressly or implied. For reference, here's the Japanese:
It translates as “In order to accomplish the aim of the preceding paragraph, land, sea, and air forces, and other war potential, shall not be maintained”.
Somewhere along the line, the English version, which is wrong, became the accepted version, the one that scholars and strategists outside of Japan relied on when thinking about Japanese politics and policy. It is in college textbooks on modern Japanese history and politics, is often cited in media reports, and referred to as a model for the rest of the world in terms of anti-war, pacifistic tendencies.
Of course, experts who know Japanese have long since seen the translation problem here. But it wasn't until recently that a change to the Japanese constitution seemed likely to happen, so this translation problem wasn't given much thought. Whether or not Japan changes its constitution does not much matter though, since Article 9 says nothing permanent.
Perhaps making this translation issue less important is the reality that Japan has the third largest, best-equipped military in the world. Though called the Self Defense Forces, they are capable of military action. Also, Japan maintains fast breeder reactors and could become a nuclear nation within twelve months of deciding to do so.
Nevertheless, the words in the Japanese Constitution are taken seriously by Japanese and other people around the word. So the next time someone says the translation doesn't matter or any old translator will do, or worse, use a machine translation system, just remember this little example. Getting it right is important. Sometimes it's globally important.