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§7.2.12

Underlined Text

Underlined text—which markup?

✅ NormativeSettled. The requirement holds as written.📄 Page ruleCan be applied from the page alone.Read §7.2.12 in the RFC ↗

The requirement

Underlined text MUST be wrapped in <u>…</u>. The output MUST NOT use <ins>, and MUST NOT use _ text _.

When it applies

Sketch of the printed page — layout, not output
subject to the <u>prior written consent</u> of the lessor

Markdown has no underline of its own, so the HTML element is used.

Reading the examples. Each one pairs a source page with the output the rule expects. ✅ Sample: the rule applies. ❌ Counter-sample: it looks like it applies and does not, or a rendering got it wrong. A non-conforming output, in red, is shown only for contrast. … marks content left out of an excerpt.

The point, in a small example

Compare an underlined replacement, an ordinary underline and a printed divider. Their positions and roles determine the output. These pages are made up to isolate the rule.

01

✅ SampleConstructedThe rule applies

A replacement underline is not an insertion-history tag

Keep the visibly struck 60 and the visibly underlined replacement 55. Do not silently discard the deleted value, infer an edit-history <ins> tag, or encode the underline as italic.

Source page
Underlined Text — A replacement underline is not an insertion-history tag. Source page.
Non-conforming output

What the rule rules out.

Markdown
Rate: <ins>55</ins>
Expected output
Markdown
Rate: ~~60~~ <u>55</u>
Underlined Text · Source page

A replacement underline is not an insertion-history tag

Underlined Text — A replacement underline is not an insertion-history tag. Source page.
02

✅ SampleConstructedThe rule applies

Underline is not italic

The entire printed sentence is underlined. Use the underline tag, not Markdown underscores.

Source page
Underlined Text — Underline is not italic. Source page.
Non-conforming output

What the rule rules out.

Markdown
_Return by Friday._
Expected output
Markdown
<u>Return by Friday.</u>
Underlined Text · Source page

Underline is not italic

Underlined Text — Underline is not italic. Source page.
03

✅ SampleConstructedThe rule applies

A printed divider is not a page boundary

Both labels are on one page with a visible divider. Use <hr/>; reserve --- for a change of page.

Source page
Underlined Text — A printed divider is not a page boundary. Source page.
Non-conforming output

What the rule rules out.

Markdown
Morning session

---

Afternoon session
Expected output
Markdown
Morning session

<hr/>

Afternoon session
Underlined Text · Source page

A printed divider is not a page boundary

Underlined Text — A printed divider is not a page boundary. Source page.

Why not the alternatives

<ins> means inserted text — an edit-history claim that a plain underline on a page does not make. _ text _ collides with Markdown emphasis and renders as italics.

Underline in a redline

An underline-only replacement in a redlined table — a new figure underlined in place of a struck one — is still written <u>1.335</u>, next to the struck value. See Struck and Replaced Values (§9.6.7) for how the pair is encoded.

More

Rule id text-underlined-text · text formatting inline