You should ask someone to check who has some experience or you can trust.
As said before: the translation in question wasn't checked because previous translations of the same translator have been checked so I assumed the translation was a legitimate one.
What's your opinion, if I create a new topic in services (like AOBT) but for checking translations for "problematic languages", where abuse has been detected? I could link any new translations before meriting and people like you could be my "trusted proofreaders": You could write a few words in that topic, if it's a quality translation or not, and I could finally approve it, when I have your confirmation.
What's your opinion of such a solution?
The idea is good and not only him but many other board members will also be able to look at it and provide their opinion. This way only the best translators will get recognition and spammers will try to stay out of this. I worked with a blogsite before where I did translations in our native language so i also have the skill of a translator and i am sure there are a few others on our local board who also have expertise in this category. You will get at least 5 to 6 expert proofreaders.