headingoffset is Not the Document Outline Algorithm

Hi, just me heading off some bad advice I’m starting to see in developer venues. Background The proposed Document Outline Algorithm, where headings would automatically reset themselves to the appropriate level based on their position in the DOM structure, was never part of a final HTML specification. It was quickly proven to be unworkable; brief support in JAWS demonstrated that. You can read the tortured history (and a JAWS support demo) in my 2016 post There Is No Document Outline Algorithm. In 2019 WHATWG worked to resurrect <hgroup>, partly in a novel effort to try to resurrect the Document Outline Algorithm. In the end, even that effort was futile. <hgroup> came back, but it came back as a grouping element only. The only impact it has on heading structures is that browser could, if they really wanted, ignore other headings in the same <hgroup>. In 2020, Steve Faulkner wrote about the doc-subtitle role, from the Digital Publishing WAI-ARIA Module 1.0, as a way to handle subtitles…