three-tiered directory structure layout

[fmyblack]

My directory structure is three-tiered, with a layout.html file at each level. I've noticed that by the third level, the override for the main tag no longer works. Why is that?
here is my directory structure:

www
index.md
layout.html
---posts
      index.md
       layout.html
      ---xxx
           abc.md
           layout.html

[nobkd]

Did you mean the <p>-tag?

Can you provide a minimal reproduction, please?
E.g. as GitHub repo / code snippets

Thank you