Is there a way to italicize comments in Visual Studio Code?

Thanks for pointing me in the right direction Victor. Putting this in my settings file (Visual Studio Code 1.42.1) did the trick:

"editor.tokenColorCustomizations": {
  "textMateRules": [
    {
      "scope": "comment",
      "settings": {
        "fontStyle": "italic"
      }
    }
  ]
}

You can see selector scopes by pressing ctrl/cmd + shift + p, and looking for Developer: Inspect Editor Tokens and Scopes.

You can apply settings to multiple scopes by providing an array:

"editor.tokenColorCustomizations": {
  "textMateRules": [
    {
      "name": "Comment",
      "scope": [
        "comment",
        "comment.block",
        "comment.block.documentation",
        "comment.line",
        "comment.line.double-slash",
        "punctuation.definition.comment",
      ],
      "settings": {
        "fontStyle": "italic",
        // "fontStyle": "italic underline",
        // "fontStyle": "italic bold underline",
      }
    },
  ]
},

Related: How do I get Visual Studio Code to display italic fonts in formatted code?