Decoration becomes expensive when it competes with the task. It asks for attention at the same moment the reader is trying to spend attention somewhere else. This article defaults to serif text, with this phrase switched back to sans.

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And

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The best interface ornament is usually structural: a rule, a margin, a rhythm, a repeated position. Inline serif and inline sans can both be used within the same paragraph.

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Yeah.

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Blah blah blah.