He uses his editor to work on texts. Then I can understand that he wants to have non mono-spaced fonts. However that would work for the text, not for the code.

He uses his editor to work on texts. Then I can understand that he wants to have non mono-spaced fonts. However that would work for the text, not for the code. So there should be a mechanism to make up the code, like with color coding, and use a different font for text if it's just text, not code.