[kevingadd]

The canonical representation of DOM content is DOMString (https://developer.mozilla.org/en-US/docs/Web/API/DOMString), which is not UTF-8. Your HTML being encoded in UTF-8 is irrelevant, it gets decoded when it's loaded into whatever the canonical representation is. Your HTML could be in Shift-JIS or ASCII or whatever and not UTF-8, same difference.

[trusktr]

This is exactly right. UTF-8 is the transmission format that your HTML gets sent in, but it is not the format of strings in JavaScript at runtime.

The problem being discussed is about runtime interoperability between JS (with WTF-16 string format) and WebAssembly.