Yes, but this application note is from 1992 and is based on an even much older application note from NS. Today (since 1996) we have CE testing and use a different approach to handle EMI. Just look how the PROFIBUS people treat this RS485 stuff. They have a secreened cable and bond the cable screen to PE at each end of cable. Signal ground is soft earthed via caps at both ends and, of course, there are no 100R resistors in the signal ground lines. Each current running in the signal ground line would develop a voltage drop across these resistors and directly create common mode noise. There's only one reason for these resistors, to deal with hum loops. But that is exactly what you don't have due to your DC/DC-converters.

Kai Klaas