# Decorative horizontal rules

Part of [The AI Tells Index](https://feedsquad.com/ai-tells). A tell signals low effort. It does not identify an author. Skilled writers produce every shape listed here, some of them daily, and automated detectors misread those writers for it at rates measured above 60 percent on non-native English prose. Nothing in this index proves that a machine wrote anything. Read an entry as one piece of evidence to weigh against the false-positive notes printed beside it.

## Facts

- Id: decorative-horizontal-rules
- Category: Formatting (formatting)
- Subcategory: dividers
- Also known as: thematic break spam, rule between every section
- Status: Active. Currently signals low-effort writing.
- Severity: low
- Evidence grade: community-observed (named by practitioners, no formal measurement exists)
- Languages: en
- Added: 2026-08-15
- Updated: 2026-08-15
- Page: https://feedsquad.com/ai-tells/decorative-horizontal-rules

## Description

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-written

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.

## Detection

Type: deterministic (a regular expression, run as written)

Scope: document

ECMAScript regular expression. The build validator compiles it and tests it against this entry's own specimens.

```regex
^[ \t]*(?:-{3,}|_{3,}|\*{3,}|={3,})[ \t]*$[\s\S]{0,800}?^[ \t]*(?:-{3,}|_{3,}|\*{3,}|={3,})[ \t]*$
```

Flags: gm

## Examples

Constructed specimens. Written for this index. Never quoted from anyone's posts.

### Specimen 1

Before, exhibiting the tell:

> What we changed this month
>
> ----
>
> We moved the export job to a queue.
>
> ----
>
> Support tickets about timeouts stopped.
>
> ----
>
> Next month we look at imports.

After, repaired:

> 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.

Note: Figures in this repair are invented for the specimen.

## False positives

Who legitimately writes this way.

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.

## Sources

1. Wikipedia: Signs of AI writing
   https://en.wikipedia.org/wiki/Wikipedia:Signs_of_AI_writing
   (tier: community; accessed 2026-08-14)
2. vale-ai-tells, 111 machine-checkable rules
   https://github.com/tbhb/vale-ai-tells
   (tier: community; accessed 2026-08-14)

## Status history

Ids are permanent. A retired tell keeps its id and its page.

- 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.

## License

CC BY 4.0. https://creativecommons.org/licenses/by/4.0/

Attribution: The AI Tells Index, feedsquad.com/ai-tells

Reuse the data, including commercially. Keep the attribution line.

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Part of [FeedSquad](https://feedsquad.com). Built by [Herman Foundry](https://hermanfoundry.com) from Levi, Finnish Lapland.