[0] https://www.w3.org/TR/2016/WD-DOM-Parsing-20160517/#widl-Ele...
Can you be concrete? (This reply doesn't really clear up anything about the previous comment.)
This contains two independent statements, (a) "If the element has no parent element, setting its outerHTML property will not change it or its descendants," and (b) "Many browsers will also throw an exception [on setting an element's outerHTML property if it has no parent element]."
Statement (b) is true, since Chromium- and WebKit-based browsers will throw an exception if the element doesn't have a parent node which is also an element. Statement (a) isn't browser-specific, and thus it is false, since on Firefox, setting an element's outerHTML will change it and its descendants if its parent node is a document fragment (which is not a parent element).
Where we differ might be that I don't see the "many browsers" qualification as applying to the first statement.
> NoModificationAllowedError DOMException
> Thrown if an attempt was made to set outerHTML on an element which is a direct child of a Document, such as Document.documentElement.
So I'd say the Notes section is simply imprecise.
The div has a parent node but no parent element, because a document fragment is not an element.