In previous threads on this topic on Meta the consensus for supporting multilingual discussions was to have separate instances for each language. However, there are use cases where people don’t want to fragment the discussion, but rather participate in one discussion, which is predominantly in English. However, on occasion they want or need to use their native language to read or respond to posts.
For this use case, I believe the user experience should not be to translate all the page content into one language but rather to allow the user to select specific posts for translation. The reason is that users still don’t trust automated translations (they are problematic with technical discussions) and prefer to muddle through a post in the native language. However, it does sometimes get beyond them and they need to resort to a Google or Bing translation. By allowing someone to select which posts to translate gives them this freedom.
I have seen this implementation once (I’m tyring to find it again) where the developer enabled Google Translate on a post by post basis and it seemed practical.