OP is asking what the content type of the body is to be interpreted as.

You're assuming HTML string, which might not always be correct. What do you do with Markdown?

You need to have a standard way to represent things like this, because otherwise it won't gain traction solely due to the immense complexity of implementing viewers.

Edit: On top of this, HTML might not necessarily be the best choice. In that case it'd just be browser wrappers galore.

Well grandparent also assumed HTML since he put an HTML tag with html attributes in his node. I'm not sure how different this is, and if he wants to convert this to markdown he'll also need a html to markdown converter.

gain traction? you are really talking about a non-issue this decade

everyone is already used to making their frontend, backend and database parse and store external things in key value pairs

this schema pre-detecting ship has sailed a long time ago