Sorry, got caught up. This is getting circular but to answer specific points:
If you do not speak the language being translated, you have no idea which translator is more accurate. One may provide a more intelligible translation as it handles the grammar of the target language better, but you have no way to know how well the source has actually been translated, because you can't read it. But really that's irrelevant. Asking users to post an English translation doesn't stop other users from translating it into another language. What it does do is make it easier for conversations to continue, stop other users from having to dig through articles to determine if it says what the poster has implied it does and, in cases where there is an issue, gives the mods something we can compared to the original article and see if the user is being dishonest in their translation.
As for posting articles translated from a language you don't speak, personally I wouldn't ever post something that I couldn't be sure what it says. However, if you want to then you just have to follow the same request and post an English translation of the pertinent parts.
Users are responsible for what they post. The point of asking people to post a translation is to show that they think the source contains the information they need to back up their claim.