How do I change the ~/.vimrc to have the comments in my code italicized?
In my ~/.vimrc file I have:
highlight Comment ctermfg=
highlight Comment cterm=italic gui=italic
You'll need a font with an italic set and a terminal capable of displaying italics. Also, if you're using a color scheme other than the default, the above line should come after the color scheme is loaded in your ~/.vimrc so that the color scheme doesn't override it.
The cterm makes it work in the terminal and the gui is for graphical Vim clients.