> The "inner 1" block is delimited by *six* equal signs. But "inner 2" is
> delimited by *eight* of them. Both are children of the same outer block.
> This is certainly bad style, but is it valid?
Based on how it's implemented in Asciidoctor, yes that is valid.
If you aren't already, I would strongly encourage you to test scenarios in Asciidoctor first. I think you will often get an answer faster that way.