I guess content translation for posts is not the right way to do it.
You can't have a discussion in more then one language. I mean, i could start here writing and explaining in german (of course only if the start post would have a german translation), but at some point some people are going to loose track of the discussion.
That's why I started with language tagging ... A simple system where you tag your discussion in one specific language. And well, if you'd like to have the same topic in another language, just make another thread.
Keep it simple. 🙂