When PageA has this content
<section begin=chapter1/>foo bar<section end=chapter1/> foo bar <section begin=chapter2/>XYZ<section end=chapter2/>
and PageB has this content
then a special page (WhatLinksHere or somewhere else) should show
Pages that link to "PageA"
- PageB (section transclusion: "chapter2") (← links | edit)
so that editors working on PageA don't have to search for which transcludes which. Otherwise, when different sections of a page are transcluded by different pages, I expect it becomes difficult to handle for editors.