I think the necessary insight here is that we want to diff type-mismatched values after serialization, which quoteWrap a) fails to convey, and b) currently does so inconsistently (e.g., it escapes " in strings by \-prefixing, but does not similarly escape \).

with

function serializeForDiff( value ) {
	// Use naive serialization for everything except types with confusable values
	if ( typeof value === "string" ) {
		return JSON.stringify(value);
	} else if ( typeof value === "bigint" ) {
		return `${ value }n`;
	} else if ( typeof value === "symbol" ) {
		const ctor = Symbol.keyFor(value) !== undefined ? "Symbol.for" : "Symbol";
		return `${ctor}(${JSON.stringify(value.description)})`;
	}
	return `${ value }`;
}

I like that solution.

I like that, too! Using JSON.stringify on strings is a great idea. ❤️

I'll try it and post some examples.

Something I realized while testing is that Symbols do not get sent over the wire (they get removed when passed through JSON.stringify). So, I moved that part to listeners.js.

Also, I switched to just show the diff all the time when at least one is non-null. I found it reassuring to confirm those are the values in diff form.