So there looks to be an error in the rendering of the Markdown code. Typically HTML statements are allowed in markdown and are interpreted correctly in the visual view. I have used this before in other markdown programs.
Since the markdown underneath does not support the GitHub checkboxes I tried to use a method to get around it:
which renders the checkbox just fine.
Unfortunately when actually creating a legal html code to complete it it is not rendered at all - . This could be an error with the markdown engine.