Steps to reproduce:

1. Have an older version of Agent installed on Windows, e.g. 7.0.0
2. put multiple hostnames in the config file
3. Download newer version with MSI, launch
4. Installer will read config file and fill in hostnames
5. Won't accept "," as a character within Host name field, can't proceed

Result:
See screenshot


Expected:
To installation complete successfully

It is very much possible this affects a wide range of versions.