> Conforming to a complex specification is not inherently a good thing

Kind of a hard disagree here; if you don't want to conform to a specification, don't claim that you're accepting documents from that specification. Call it github-flavored YAML (GFY) or something and accept a different file extension.

https://github.com/actions/runner/issues/1182

> YAML 1.1 to be an important goal: they still don't support merge keys

right, they don't do merge keys because it's not in YAML 1.2 anymore. Anchors are, however. They haven't said that noncompliance with YAML 1.2 spec is intentional

> Call it github-flavored YAML (GFY) or something and accept a different file extension.

Sure, I wouldn't be upset if they did this.

To be clear: there aren't many fully conforming YAML 1.1 and 1.2 parsers out there: virtually all YAML parsers accept some subset of one or the other (sometimes a subset of both), and virtually all of them emit the JSON object model instead of the internal YAML one.