When using special UTF-8 characters like äöüß (quite common in the german language, not sure if the problem is the same with œæå from scandinavian languages for example, but I suspect it to be the same), the Companion App Chat won’t show the chat message but displays an empty chat message instead. This is quite annoying on international group rides and frankly renders the companion app kind of useless when it comes to chatting.
If you find this annoying too, please vote this up, so Zwift Support will get on it.
I already submitted a ticket, but feel free to submit one as well.
This was tested on iPhone6s with iOS 13.2.2 and Companion App 3.9.0
I’ll attach some pictures: