Zwift is having some problems with special characters in names. If you have a name like mine (mine is René Løwe Jacobsen), then it’s going to change the special characters into mojibake. The problem exists on both Windows and OS X.
Could this be because you rely on the system region (and encoding) to be the same as it is on your system?
René, I have the same issues as you. My name in Romanian is Ștefan Roșu, but in the Zwift app it is displayed with strange characters - in the browser Zwift Profile it is displayed ok.
Any solution/workaround for this problem?
No, I have not found a solution and I am pretty sure that it can only be fixed by the zwift team. So we have to wait for them. 
But a workaround could be not using the special characters until it is fixed.