I appreciate that this suggestion could lead to a flood of low value translation posts, and I hope that anyone considering posting translations will be responsible, and only use exceptional posts for translation. Obviously if this concept is abused, it will be banned, and I think that will be a loss to all of us.
Translating the post and quoting the original one should be ok and it should be acceptable to the original author also, as long as the translation is exactly the same. Of course all the credit goes to the original author. But translator can be appreciated for putting efforts in translating and bringing some thing interesting or valuable to the local community.
Now regarding the copyrights claims, if proper reference is provided then there should not be any copyright concern. For example if I take a screenshot of any post from this forum with the author clearly visible and put it on twitter with translation into my native language. I'm not breaking any rule here, since it was posted on the public domain, I did not steal the content and I'm publishing exactly what was posted. Same can be applied to translated posts with original post quoted inside.