There are some really interesting points in this article, and the re-design of emacs is something I remember seeing on the /r/emacs sub-reddit a while ago. It looks really good!
I’ve yet to try the design out myself, but some day I will.
The active emacs theme following this article sees to be here: nano emacs.
It’s from https://github.com/rougier/elegant-emacs which is a precursor of the nano emacs theme. I tried to run it but in the end it took away too many UI elements that I was actually using.
Worth mentioning the modus-themes package (https://protesilaos.com/emacs/modus-themes), which introduces a color scheme for maximum accessibility. It will be included in emacs 28, but is probably too recent to be mentioned in the paper.
My key personal reflection is the number of things which I do because they bring me joy rather than actually being better. E.g. I use neon rainbow highlighting because it makes me happy.
I think he’s overstating the absence of margin for code because a majority of code bodies (as opposed to the header-like signatures), have at least one level of indentation, and 4-spaces looks a lot like standard margin. Right margin is more challenging because you want to be careful when reflowing code, and if your window width exceeds your max column count you get a kind of natural right margin.
The left window of inline comments was an interesting idea both visually and as an example of user style overriding the text representation of the code. I don’t often use inline comments because in the code that I write, it usually deserves paragraphs or sentences, or indicates a defect in the code, but I’m not sure how to inline edit that window since I can’t go to end of line anymore.