Bug#1026986: console-setup: "Dead" keys do not work for Greek keyboard layout in tty

[Παύλος Γκέσος]

> Ah, you mean that currently, shift-w produces Sigma, but that's not
> actually useful, so we can just make it a dead key for ̈́?

Exactly!
This is what Microsoft Windows does.
Probably the Windows kernel has the same limitation too :-)