No, Parser.HTML has always _explicitly_ allowed quoted attribute names
Where is this documented? Why would anyone use it?
(it sets the allowed quotes to the same thing for both attribute values and names).
I know this is fairly odd, but so is the more-than-one-quoted-string syntax.
<t "a"='a''b'c'"d> would return ([ "a":"abcd" ])
Really? That doesn't even have matched quotes...