That seems to ignore the conventional wisdom that according-to-Hoyle XHTML was a DOA standard because it mandated error handling in ways that no browser implemented and most of the authoring community didn't want. Authors don't write well-formed XML, even today.
XHTML 1.0 didn't mandate so-called "draconian error-handling", it just offered it as an optional feature.
XHTML 1.1 (which was released but noone used) and XHTML 2 (which was never finished nor released) did mandate it. I wasn't a big fan of that decision, I don't think it would've worked, but XHTML 1.1 was still very usable while ignoring that one requirement; throwing out the baby with the bath water was a massive overreaction on the WHATWG's part.
XHTML, other than Transitional, which nobody should count as "implementing XHTML", is an XML application. It inherits XML's parsing model. Every error is a fatal error.
IIRC several major browsers implemented XHTML error handling, but only for documents with a Content-Type: application/xhtml+xml header, which was basically nothing because that would then trip up other browsers
Opera had the "draconical" approach, where upon the error you just had that, an error. Firefox, iirc had a softer approach where you still got the page rendered, but you'd get the error reported too. Anyway it all depended on the proper MIME type for the XTHML (as it should). However the whole MIME type and everything associated with it (some elements and APIs are treated differently) is a whole barrel of worms, so XHTML in any of the incarnations was never a good idea.
