Gary,
Sorry, this bug is fixed in the github version but not in the quicklisp version (darcs).
The bug was in utilities.lisp, function process-brackets with the variable buffer-count not being incremented
BTW: in order to load the github version I had to comment this line #-asdf-system-connections :container-dynamic-classes from cl-markdown.asd. I don't know where this system is defined.
andy