This answer is more of a hack than a real solution to your question.
From the text you show, it seems you may rely on indentation for your folding.
If so, you can use set foldmethod=indent.
A little function I use in such case:
It would be really hard to do reliably.
Basically, if you brave enough, check what current markdown plugin uses for folding and try to rewrite it:
:set foldmethod? to find out if it is expr or not
:set foldexpr? to find out what is the function name expr uses
create your own MarkdownFold() function (or whatever name is 2. showed)
So you would end up copy ...