If people on this mailing list are so concerned about other people's umasks, then I would suggest a great starting point would be to start by making it POSSIBLE for other people to set their umasks the way they want.
If you use a Desktop Environment, go to your DE's support mailing list, and ask them how to set your umask so that it works as expected in all of your programs. This must include programs that are launched at login, and programs that are launched by a menu or icon, and terminal emulators (and not merely the shells that run inside terminal emulators). Make sure whatever solution they give you applies regardless of whether a program is launched as a child of a window manager, or a child of a systemd user session, or a child of dbus. If they can't give you a solution that works in all of these cases, **make them fix their stupid software**. Do not let up until they have given their users a way to configure their environments as needed. Once all of the Desktop Environments provide a way to do what you want, **then** you might think about leaning on Debian to change their defaults. That will be a separate battle, but it's not a battle you can currently even **begin** fighting. Also bear in mind, this is the Debian **user** mailing list, and none of us have any power whatsoever over the Debian project. Let alone over the various Desktop Environments.
