IE's XHTML Compatibility

Question

I'm having a rather heated debate into IE's XHTML Compatibility. The only thing is, I'm unsure if the guy is trolling.

Essentially he claims that IE has absolutely no XHTML compatibility, and that a document with a defined XHTML doctype means absolutely nothing when served as content type text/html, regardless of the browser used.

I do not believe this and sources say otherwise, but I am wrong?

Edit: Disregarding IE, does it still mean that when XHTML is defined in an HTML document it is NOT XHTML? Like the guy suggested? My current understanding is that XHTML is often contained within the HTML content type. This means that technically you could say that XHTML is merely HTML unless the correct content-type is used. But it's still XHTML syntax and so it a little confusing.

You can find the thread in question over at digitalpoint forums.

Answer 1

IE has indeed no support for application/xhtml+xml content type while other browsers would then handle HTML as XML. When text/html is used, every browser will just handle XHTML as HTML, IE does nothing different here (expect from the usual quirks).

More details here: http://hsivonen.iki.fi/doctype/