heading level order

All,

My name's Ian Stewart, I'm a GWT/Drupal developer and new to accessibility, but I've done extensive research lately in order to make one of my projects as accessible as possible.

Right now, I'm confronted with an interesting issue regarding heading levels.  Heading levels, from my point of view, have always been primarily a visual style cue.  Often an <h4> works better for CSS inheritance reasons than an <h3>, for no reason other than visual style.

Recently, our accessibility tester approached me with an interesting point.  She suggested that the reader is expecting heading levels to make sense as if the page is a linearized document, with each depth representing a consistent level of detail.  What do you all make of this statement?  Does jumping from an <h2> to an <h4> on a page for stylistic reasons truly lessen the intuitiveness of the page for a screen reader?  Is subclassing an <h3> to fit my style needs worth having <h2>s always followed by <h3>s?

Thanks for your thoughts, I found it an interesting question.

Sincerely,

Ian