Perhaps screen readers can be set to read out the major headings to help people figure out what part of the document they want to read. This would have a level of detail or verbosity control.

First you read h1, find the right header. Then h2 with 2 levels of detail, which hits h2 and h3. You miss the sub-section you wanted because it was marked h4 instead of h3.

It's a broken tree structure... that'll cause problems any time somebody wants to do a logical traversal.

Yes. Screen readers load the page contents into a buffer and allow users to scan headings, links, etc. having a broken outline structure is potentially confusing [1]. This is also why descriptive linked text is important (ie: no "click here") [2]

[1]: http://www.w3.org/TR/WCAG20-TECHS/H42.html [2]: http://www.w3.org/TR/WCAG20-TECHS/H30.html

Screen readers do indeed have a feature that allows the users to browse just the headings.

As others have mentioned, it's likely flagged as an accessibility issue since having an h4 follow an h2 indicates a broken document structure.

It's also probably included in the tool because things like that usually (though not always) mean that the developer is just using the h4 tag based on how it looks as opposed to actual semantic meaning, and the tool is designed to get you to put more thought into what you're actually building.

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