Since inline TOCs are only needed for Kindle books, why not follow Amazon's recommendation and use divs?
Their publishing guideline recommends the following:
Code:
<style>
div.chapter { margin-left: 1em}
div.subchapter { margin-left: 2em}
</style>
<div>Section 1</div>
<div class="chapter">Chapter 1</div>
<div class="chapter">Chapter 2</div>
<div class="chapter">Chapter 3</div>
<div class="subchapter">Subchapter 1</div>
<div class="subchapter">Subchapter 2</div>
<div class="chapter">Chapter 4</div>
<div class="subchapter">Subchapter 1</div>
<div>Section 2</div>