Ken Arromdee wrote:
Besides, you're choosing a very strained interpretation of the rule. I would say that a "common English name" is a word that has become part of the English language, and can be found in dictionaries and similar places. A character or a sword in a manga would have no common English name at all.
Well, it can also include translated proper names, not just things that have become part of the English language and show up in dictionaries. The "use common names" rule is strongest when something /actually/ has a common English name, though.
In cases where a particular English translation is well established, we use it even if it could be argued that it's somehow "wrong"---for example not everyone is happy with the title [[The Stranger (novel)]] as a translation, but it's so well established as to be obviously the right place to put the article. The same goes for lots of other novels, works of philosophy, etc., that have conventional but in one way or another "wrong" English translations to which a minority of people virulently object. In a different example, we also tend to use Western name order for famous individuals who are conventionally referred to in that order in English media, and use nonstandard transliterations of personal names if they've become standard in English for that person.
In the case of this sword, though, it'd be hard to argue that there's a particularly "common" translation or "standard" English name, so some sort of more systematic/mechanical transliteration is probably best. That's also what we also do with more obscure real people who don't have clearly established English versions of their names.
-Mark