Here is a weird bug (or unexpected feature) in the MarkDown engines, probably tex related.

     ($ \{a,b\} $) now you can never leave the code block.
Not on a new line.

Not in a new paragraph.

You are forever in the code block.

Until you say the magic word, open-parenthesis dollar-sign: ($
New line for a new world.

New paragraph to celebrate the new me.