What's the source for this, I do see they're the CSS co-designer, was this requirement originally written somewhere? I'm looking at the description of important, and I don't see this intention carried through.
If the intention is indeed as described, then the CSS designers failed to communicate it properly, and not "a sign you may not understand the cascade properly."
https://www.w3.org/TR/css-cascade-5/#important
https://www.w3.org/TR/css-cascade-5/#importance
If the intention is indeed as described, then the CSS designers failed to communicate it properly, and not "a sign you may not understand the cascade properly."