First-line indent and a blank between paragraphs are mutually exclusive conventions

What it is

Western print signals a new paragraph with a first-line indent; the blocks still sit tight. Screens and much Chinese web body cut paragraphs with a vertical gap and leave the first line flush. Each convention is complete on its own. Indent plus gap on the same page says the break twice, the two cues compete, the page thins, and the signal does not get clearer. They are exclusive. They are not two kinds of emphasis you can stack.

Why it happens

A paragraph break needs one stable signal. An indent offsets the first line from the left edge; a gap in that edge is enough, and it costs no vertical space. A vertical gap cuts the rhythm while keeping a flush left, which fits narrow screens, link-heavy copy, and short paragraphs — short paragraphs indented make a dense field of shallow notches that scan as noise. Fire both at once and the signal saturates: readers cannot tell whether a gap is a paragraph or a topic change, short blocks look like list items, long prose looks like a stack of cards. Chinese print traditionally indents one or two characters; Chinese web body usually gaps. The double import happens when a print manuscript is pasted into an interface with both habits still on.

Where it stops holding

Block quotes, lists, and the first paragraph after a heading often skip the indent; that is an exception inside one convention, not a mix. Mail and chat bubbles are not paragraph conventions; do not “correct” them with indents. A magazine that indents inside a column and gaps between columns is using two levels, not two systems on one level. Teaching materials that must show both historical habits should use separate specimens, not mix them in one lesson.

Applying it

• Pick one: long-form, print-like reading indents with paragraph spacing at zero (or equal to leading); UI, help, and settings copy gaps with no first-line indent.
• Search the file and the stylesheet for text-indent and a non-zero padding-bottom on paragraphs. If both are live, delete one and check that the break still holds.
• When a print PDF becomes an interface, drop the indent first, then decide whether a gap is needed. Do not paste both.

Related

• Same group: F4.13.1 Paragraph spacing must exceed leading or the break cannot be seen · F4.13.3 A long unsegmented block drops reading completion · F4.13.4 Paragraph spacing should track leading, not a fixed pixel value
• Nearby: F2.04 Whitespace · F4.05 Alignment
• Search terms: first-line indent · paragraph break · block spacing