Because if he only translate it and post the translated text its not a plagiarism in my eyes !
That's correct if he uses his own words to redact the post. But if he use an automatic translator and post it as it is word by word then it is plagiarism.
It is just another trick to avoid getting caught.
It's still plagiarism if they don't post a link to the original imo.
This is what is often done legitimately... If they'd just added a reference link then it wouldn't be plagiarism imo and they'd probably get merits for it still.