One trick that I try to teach the users on our site that want to do advanced Markdown or see how some advanced HTML feature was done is to use the raw view of the page.
This is the URL to the preceding post: https://meta.discourse.org/t/more-than-two-levels-of-details/152421/4
This is the URL to the preceding post as raw: https://meta.discourse.org/raw/152421/4
If you look at the columns of the posts table in PostgreSQL you will see there are two columns that hold the text for a post, raw and cooked. raw is the text as entered by a user and typically contains the markdown and HTML as entered by the user.
However when you see the post as normally displayed it has been cooked to some degree and you can not see the raw text, even if you use the Internet browsers ability to reveal the HTML.
Now sometimes one can use the menu items in the edit menu bar to drop some template HTML into place and sometimes you just have to do it by hand.
HTH
EDIT
For all the theme creators.
A theme that adds a button to view the post as raw would be nice. The theme should have a configuration option to limit visibility of button based on trust level or categories.
EDIT
For those wanting to see the Raw post button theme (noted below) working on a more complex page see the SWI-Prolog Discourse page: Post for testing installed component themes and plugins
Note: Since anonymous users can not see the raw button, you will need to simply join.