tldr:
* I installed console-only Debian on an old laptop (no desktop OS at all)
* I added some packages to make it work better for writing:
* network-manager for connecting to hotspots while I'm away
* kmscon for custom fonts and more than 16 colors in the tty
* tmux for a nice status
The answer is right there in the fist paragraph, and in more detail if you read the whole article.
The author uses kmscon, that is a usermode console with proper graphics drivers, hi res rendering, and UTF8 font support. There is no desktop environment used.
I suspect that is where the italics support is coming from. Makes me want to try it out.
https://en.wikipedia.org/wiki/Kmscon