They had the following, which is indented by 4 spaces:
<p>Thanks for Any Help!!!</p>
And in your edit you removed the 4 spaces in front of it (to be fair you could have probably removed the entire line, as it's noise, although you'd have had exactly the same issue).
So, it seems the site checking mechanism just ensures something in the post is indented by 4 spaces, and so deems there to be code present.
I'm not sure what can be done about it, as it's impossible for the site to identify if code is real or not, as there is gazillions of code possibilities.
I guess this is just one of those checks which probably catches "most" people (although potentially less now this post is here).
I've edited the post.
I was going to add the code, but the code and link to Codepen are not relevant anyway, as the question is essentially just asking how to add code/theme to Wordpress.
So I just removed the link and commented to the OP.