Interesting, again. Of note:

"...length of the slug must be between 1 and 255 characters..."

A byte, path depth, ? Hmm...

"...provide this in the metadata without actually having an image in the blog post..."

Custom thumbnails, anyone?

..."format seems to be either "markdown" or "html", depending on the content..."

Interesting, but, I wonder; I've made posts with mixed markdown & html tag content, which is necessary if you wish to make use of <div>s, for example:

### [useful resource](https://steemit.com/@neuromancer)
<div class=pull-right>https://steemitimages.com/DQmQMZPRjgWkSdhQZMYrmtm6PU9sS1HKSpVHzmjTXp9j2Se/noteymcnoteface.png I will show you how to make some text that will wrap the noteymcnoteface.png image but also has bold and italic HMTL tagged text in it. 
 
 In fact, I'm about to publish an article on it to help you all achieve advanced formatting for your work :]

Produces:

useful resource

I will show you how to make some text that will wrap the noteymcnoteface.png image but also has bold and italic HMTL tagged text in it.

In fact, I'm about to publish an article on it to help you all achieve advanced formatting for your work :]