Selectors and case-sensitivity

[fantasai]

I'm going through the incoming references to Selectors and I had a question: why does HTML specify that CSS's syntax is lowercased, HTML's tag/attribute name is lowercased, and then a case-sensitive match is performed rather than simply saying that HTML's attribute/tag names are considered ASCII case-insensitive? (From my perspective it's really weird for the HTML spec to be manipulating CSS/Selectors syntax rather than merely classifying HTML things as case-sensitive or ASCII case-insensitive.)

[annevk]

HTML element names are case-sensitive. E.g., document.createElementNS("http://www.w3.org/1999/html", "VIDEO") is not an HTML video element and shouldn't be matched by a video type selector.

[annevk]

(I think this does mean that you cannot match such elements within an HTML document environment, but that was considered an acceptable loss.)

[zcorpan]

The underlying reason is #991 (comment)

[annevk]

#2738 is also related (and undecided still it seems).