Comment by Timwi

Okay, I guess I got a fair bit of the details wrong. However, there's one detail I want to push back on:

> In addition, [XHTML1] defines a profile of use of XHTML which is compatible with HTML 4.01 and which may also be labeled as text/html.

If you read this carefully, you'll see that it's not saying that text/html can be used to label XHTML. It's saying that you can use text/html if you write your XHTML in such a way that it's compatible with HTML 4.01, because the browser will parse and interpret it as HTML.

You're correct that the doctype wasn't the reason it was treated as tag soup. It was instead because of the parts of XHTML that are not directly compatible with HTML 4.01.

The mismatch between local files and websites served as text/html was very real and I experienced it myself. It's curious that you'd think I'd make it up. There were differences in behavior, especially when JavaScript was involved (notably: Element.tagName is all-uppercase in HTML but lowercase in XHTML) and it is absolutely the case that developers like myself blamed this on XHTML.