## What it does
Flags `[label]: …` link definitions that share a label (case-insensitive, normalised) with
another definition in the same document.
## Why
CommonMark says the first definition wins; later duplicates are silently discarded. The author
usually intended for one of them to be a different label, so a duplicate is almost always a
copy-paste mistake. Worse, the discarded definition often documents the intended target, so
the link still resolves, but to the wrong URL.
## Example (bad)
```markdown
See the [docs][readme] and the [tutorial][readme].
[readme]: https://example.com/readme
[readme]: https://example.com/tutorial
```
## Example (good)
```markdown
See the [docs][readme] and the [tutorial][tutorial].
[readme]: https://example.com/readme
[tutorial]: https://example.com/tutorial
```
## Configuration
- Disable inline: `<!-- mdwright: allow duplicate-link-label -->`.
- Disable in config: `[lint] ignore = ["duplicate-link-label"]`.
- Severity: non-advisory.
## References
- [CommonMark §4.7: Link reference definitions](https://spec.commonmark.org/0.31.2/#link-reference-definitions).