Description
See https://blogs.msdn.microsoft.com/doronh/2006/11/14/where-did-my-debug-output-go-in-vista/
as well as https://git.reactos.org/?p=reactos.git;a=blob;f=reactos/ntoskrnl/config/cmdata.c;hb=6f6999647ab23b1ee53550b6f6196c912b03334a#l789
for more information.
Note also that Kd_DEFAULT_MASK is only used in the gcc kdbg debugger: https://git.reactos.org/?p=reactos.git&a=search&h=HEAD&st=grep&s=Kd_DEFAULT_MASK ,
while it should be also used in the WinDbg kd(64) debugger too.
In the latter however we only use the Kd_WIN2000_Mask. To be analysed further...