Read the original post again, please.
This local filter cap as you called "bypass cap" also acts as the LOCAL return signal path for EACH chipamp board. So the signal return is completed locally on each board.
The stopper diodes is to stop the DC back up from other chipamp board. This is exactly what the original poster has done & it is the
proper way to go.
The stopper diode is block off DC back up, & is "linear" as long it serves as a DC path with forward bias.
You're confused, pal.
c-J