I've seen this style used to raise the contrast between comments and otherwise. Though I am surprised it works in Vim given that most terminals can't render multiple fonts at once. Are there control characters for that?
IIRC the monospace font itself would have the cursive characters as its "italic" typeface, then the terminal would just need to be sent the control characters for italic text (i.e. https://rubjo.github.io/victor-mono/)
It can be tricky to make it work in Vim + Tmux etc., but it can be done provided the font includes it as normal italic typefaces. I use Victor Mono and iirc it's available in two variants depending on whether you want normal italic font or cursive.
I've been using it for a while now, can't say it makes a big difference(both positive or negative), but it kind of looks nice which is the point in the end.
