I tried it out on Office 2016/365/15.25 whatever on OS X. It works when writing data out. That's great news! And they also put it high up in the possible format

I tried it out on Office 2016/365/15.25 whatever on OS X. It works when writing data out. That's great news! And they also put it high up in the possible formats to output. Unfortunately, to open the UTF-8 file again, it doesn't work ("北京市"). You have to make a new workbook and then import the csv in, specifying UTF-8 csv. It's pretty messed up but at least it's possible now.