I think this is a bug. The v3 API shouldn't translate/convert punctuation into Chinese characters when translating en to zh. For example (http://abc.com) becomes （http：//abc.com）, which ruins the markdown syntax.
It should leave the punctuation as is or at least add a parameter in the API for users to decide.

I know there is a class=notranslation but that's not flexible for plain text and adds complexity as well.