(Love the tool by the way. Nice work. )
The issue is a template literal function that is returned by a function.

import {html, htmlBuilder} from './mySanitizer'

// The following works

const str = html`<div>${content}</div>`

Below does not work. It kind of works but blows out the syntax highlighting for the rest of the file. 

const str = htmlBuilder(this).html`<div>${content}</div>`

My fix is htmlBuilder(this).html/*html*/`<div></div>`

I'd like to not have to add the comment.

The issue is a template literal function that is returned by a function causes the rest of the page to change in subtle ways.