Decorative horizontal rules
- Id
- decorative-horizontal-rules
- Status
- Active
- Severity
- low
- Detection
- deterministic
- Evidence grade
- community-observed
- Languages
- en
- Added
- 2026-08-15
- Updated
- 2026-08-15
Currently signals low-effort writing.
What it is
A rule drawn between every section of a piece short enough not to need one. The count of rules against the count of sections is the tell, not the presence of a rule.
Why it reads as machine-made
Wikipedia records chatbots inserting a thematic break between each section of a text and notes that the habit comes out of Markdown output, where a break is cheap and looks like structure. In a short piece the rules outnumber the ideas, and the reader gets a set of boxes instead of an argument.
Specimens
What we changed this month ---- We moved the export job to a queue. ---- Support tickets about timeouts stopped. ---- Next month we look at imports.
We moved the export job to a queue after the 90-second timeout started firing on accounts with more than 20,000 rows. Support tickets about timeouts went to zero the week after. Imports are next, and they sit behind the same 90-second ceiling.
Figures in this repair are invented for the specimen.
How it is detected
- Pattern
- ^[ \t]*(?:-{3,}|_{3,}|\*{3,}|={3,})[ \t]*$[\s\S]{0,800}?^[ \t]*(?:-{3,}|_{3,}|\*{3,}|={3,})[ \t]*$
- Flags
- gm
- Scope
- document
Who writes this way legitimately
Long essays and manuscripts use a rule for a real scene break, and one divider between the two halves of a piece is ordinary craft. Newsletter and email templates draw rules under headers and above footers automatically, and the writer never sees the markup. Documentation generators emit them between generated sections. A reviewer counts rules against sections: one break in a 3,000-word essay is punctuation, and a rule under every 80-word block is decoration standing in for structure the piece does not have. Judge the ratio and nothing else.
Model attribution
Unassigned. Wikipedia describes the habit as common in Markdown output without naming a vendor, and no measurement of divider use by model family exists in anything this project read.
Platform notes
- wikipedia
- The guide keeps dated examples in which a break sits between every section of a draft, which is how the ratio became legible rather than the presence of one rule.
Status history
| Date | Status | Rationale |
|---|---|---|
| 2026-08-15 | Active | Active and cheap to check. Wikipedia documents the habit with dated article examples in which a break sits under every section. The pattern requires two rules within 800 characters, so a single genuine scene break never registers. Regex verified on 2026-08-15 against its own specimen and three negatives, one of them a text carrying exactly one break. |
Sources
- 01Wikipedia: Signs of AI writingcommunityaccessed 2026-08-14
- 02vale-ai-tells, 111 machine-checkable rulescommunityaccessed 2026-08-14
CC BY 4.0 / The AI Tells Index, feedsquad.com/ai-tells