And there is another effect. Having a bus that outputs to the master input bus shows that the signal is silenced as soon as you insert an AUX send to the master bus, even when the AUX send is not activated. The silence is permanent for the session. Removing the AUX send or reconnection the bus's output to master input doesn't break the silence.
This applies both for main and xcopyinbuf.
EDIT: yes, I know that connecting a bus to master input isn't recommended but maybe this information helps a bit.
And there is another effect. Having a bus that outputs to the master input bus shows that the signal is silenced as soon as you insert an AUX send to the master bus, even when the AUX send is not activated. The silence is permanent for the session. Removing the AUX send or reconnection the bus's output to master input doesn't break the silence.
This applies both for main and xcopyinbuf.
EDIT: yes, I know that connecting a bus to master input isn't recommended but maybe this information helps a bit.