Steps to reproduce. Run the following program using ts-node or similar.

import { format, applyEdits } from 'jsonc-parser';
const JSONString = `{"hello": \t"\tworld"}`;
const edit = format(JSONString, undefined, { insertSpaces: true});
const res = applyEdits(JSONString, edit);
console.log(res);

We would expect the following output

{
    "hello": "       world"
}

But we actually get

{
    "hello":    "       world"
}

Interestingly, if we remove the tab inside the quotes, the tab outside is removed as expected. This seems like an error since formatting should only care about tabs outside quotes.