Opening brackets and quotes must not end a line

What it is

Opening parentheses, opening quotes, the first half of a title-mark, some prefix signs — these are doors into the next span. Left at the end of a line, the door is on one line and the room on the next. Kinsoku line-end prohibition forbids those openers from closing a line: take them down to stand with the copy they introduce.

Why it happens

An opener promises that the enclosed content follows immediately. A line end is a place of closure; parking the opener there drops the promise for a beat, and the reader carries an unclosed gate to the next line. Greedy wrap only sees leftover width. Openers are narrow, so they often still fit at the tail, and the width calculation actively breaks the prohibition. The symmetry with line-start kinsoku is exact: closers must not open a line, openers must not close one. The remedies are symmetric too — carry the opener with the next character, or compress the line slightly to pull that character up. Fixing only line starts leaves the other half: in a narrow column, openers at the tail and clause marks at the head arrive as a pair.

Where it stops holding

Brackets in maths and code often have to align with operators; kinsoku yields. Slashes and question marks in URLs and paths are not Chinese openers; wrap them as URLs, not as title-marks. Closing quotes and closing parentheses are closers and belong to line-start kinsoku; they do not go on a single “punctuation must not end a line” list with openers. Latin opening quotes are sometimes hung outside the measure; hanging a Chinese title-mark that way fights the em grid.

Applying it

• Turn on line-end kinsoku with the line-start rules, covering opening brackets, opening quotes, and the first title-mark. Do not only ban periods at the head.
• In dialogue- and quotation-heavy copy, inspect the last visible character of every line. An opener there is a hit.
• If carrying the opener down leaves an ugly hole, keep opener-plus-next-character as an unbreakable pair rather than stretching the whole line’s tracking.

Related

• Same group: F4.14.1 Closing CJK punctuation must not start a line · F4.14.3 Kinsoku needs an engine; a naive wrap will break it · F4.14.4 Mixing fullwidth and halfwidth punctuation throws the beat off
• Nearby: F4.03 Measure · F4.12 Tracking and word spacing
• Search terms: kinsoku · line-end punctuation · opening bracket wrap