On a wiki page a "section" is a HTML heading element (H2, H3, etc) followed by text using any type of formatting, up to the next heading element. It generally consists of an "editsection" DIV if they are enabled, followed by a P element containing an anchor presumably for the TOC etc, then the content - which may contain subsections.
Now if each section was wrapped from start to finish in an HTML DIV it would make it much easier to implement such things as section-folding or giving various kinds of sections special colours. To do this now involves parsing the entire "bodyContents" and rebuilding it with such DIVs inserted - a slow and uncertain process.
Even better would be an outer DIV including the H tag and an inner DIV beginning after the H tag.
Another enhancement would be to auto-generate and ID for each section and subsection based on the contents of the owning H tag, perhaps including its parents in the case of subsections.