[css-flexbox] Be a little clearer in author conformance criterium.

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extra : rebase_source : e4c99898f8759135b0a301f0bb279f23a3f14b64
Add rules for attention-grabbing normative advisements.

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extra : rebase_source : bb11d44e0193964292a8dc51c8a83287940bd0d7
[css-text] Make some author conformance statements a bit more in-yer-face.

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extra : rebase_source : 86420d841da8028326d3027ab10fc27ae0e9e071