This excerpt is interesting:

"One thing I found problematic with WeChat is that unlike Hangout, for example, it doesn't store any of the conversations on the backend. There's apparently a “we're not spying on you” angle to this with regards to Tencent providing this service to users."

Yeah, but then just a couple of paragraphs before, they were mentioning how WeChat provides translation services inside the app. I highly doubt that this is being handled in the device itself.