One Emphasis Signal at a Time
SHOULD: Emphasize with bold OR italic, never both on the same text, and never underline for emphasis — on the web underline means link. Reserve underline for links, bold for strong emphasis, italic for titles/terms/mild stress, each used alone. Stacking emphasis markers cancels the contrast they exist to create.
Emphasize with bold OR italic, never both at once, and never with underline — on the web, underline means link
<strong>important</strong> · <em>term</em> · <a href="…">link</a>
// not: <span class="font-bold italic underline">…</span>Bad
Good
Why it matters
Emphasis is a contrast, and contrast only works while it is scarce. Stacking bold and italic on the same words does not make them twice as important — it makes the line look like it is shouting and spends the next level of emphasis you might have needed later. Pick one: bold for strong emphasis, italic for titles, terms, and mild stress. Underline is worse than redundant on the web, because it is the near-universal signal for a link: underlining for emphasis trains users to click text that does nothing, and it collides with design-underline-from-font, which is about styling the underline on actual links.
Reserve underline for links, and use bold and italic one at a time. This is the character-formatting version of the over-signalling failure the corpus flags elsewhere (design-ibelick-color-restraint for accent colour, content-impeccable-em-dash-overuse for punctuation): more emphasis markers do not add emphasis, they cancel it.