Quoting https://brand.systemd.io/#:~:text=Yes,%20it%20is%20written%2...
"Yes, it is written systemd, not system D or System D, or even SystemD. And it isn't system d either. [...]"
"Yes, it is written systemd, not system D or System D, or even SystemD. And it isn't system d either. [...]"
[TIL - it's not even as old as me!] https://australianfoodtimeline.com.au/1978-launch-of-big-m/
By the way, I love that the OP used the Text Fragment (Scroll-to-Text Fragment) feature. I hope it is going to catch on more, quite helpful / useful.
Anyway, why would someone use the spelling with upper D beats me. It's not proper English.
Entirely different thing. Software/things are not the same as people.
> why would someone use the spelling with upper D
SystemV, Zyklon B, Vampire hunter D, Plan B, Model T, Type O, ... It's extremely common.