Good dark themes are generally softer than this. This is way too dark. Also, the identicons (default avatars) look out of place in dark mode.
Other examples include their insistence on pixel-thin icons which are barely legible when reduced [1], flat buttons that are just colored boxes devoid of even basic button affordances, hard edges everywhere, and nearly 100% saturated colors that are an assault on the eyes.
They've never been very good at UI, but where they are these days is just bad. Their new Fluent design language [2] on mobile looks like an improvement from Metro, they're actually seeing what others are doing and copying it decently enough, but its not really out there much in their products.
[1] example here https://medium.com/microsoft-design/evolving-the-microsoft-f...
PS. In fact, it's more likely it was the Github's old design team, not MS.
PS. I've been using this one for years and it looks much "softer" on the eyes: https://poychang.github.io/github-dark-theme/
Hope it's still work in progress
It is about what feels better on the eyes
Dark theme, and at night you want to reduce eyestrain by reducing the blue light
This dark theme is full of blueish tone, wich goes against the need of dark theme
We can discuss the blue light aspect in its own merit.