Readit NewsNetscape Navigator did, in fact, reject invalid HTML. Then along came Internet Explorer and chose “render invalid HTML dwim” as a strategy. People, my young naive self included, moaned about NN being too strict. NN eventually switched to the tag soup approach. XHTML 1.0 arrived in 2000, attempting to reform HTML by recasting it as an XML application. The idea was to impose XML’s strict parsing rules: well-formed documents only, close all your tags, lowercase element names, quote all attributes, and if the document is malformed, the parser must stop and display an error rather than guess. XHTML was abandoned in 2009. When HTML5 was being drafted in 2004-onwards, the WHATWG actually had to formally specify how browsers should handle malformed markup, essentially codifying IE’s error-recovery heuristics as the standard.
This is clear in Tim Berners-Lee's seminal, pre-Netscape "HTML Tags" document [0], through HTML 4 [4] and (as you point out) through the current living standard [5].
[0] https://www.w3.org/History/19921103-hypertext/hypertext/WWW/...
[4] https://www.w3.org/TR/html401/intro/sgmltut.html#h-3.2.1
[5] https://html.spec.whatwg.org/multipage/syntax.html#optional-...
[1] https://mathenchant.wordpress.com/2025/04/21/is-1-prime-and-...
HTML has become more and more bloated. How many methods do we need to do something that was possible back in the 90s?
The accident of history is less that ASCII happens to be 7 bits, but that the relevant phase of computer development happened to primarily occur in an English-speaking country, and that English text happens to be well representable with 7-bit units.
Panel 1 Waiter: "Sir, I’d like to ask you to take off your cap in this restaurant." Smurf: "Take off my cap? You’re not asking me to take off my pants, are you?!"
Panel 2 Waiter: "That’s not the same." Smurf: "That is the same."
Panel 3 Cook (to waiter): "Let him put his cap back on." Waiter: "That’s maybe better."