[talldan]

I think there's some confusion in your comments. The HTML comments aren't a templating language, there's no (or little) post processing when displaying this content.

They're annotations that indicate where a 'block' of content starts and ends.

The JSON data stores some values set by users for a block that can't easily be parsed from the HTML content.

The content is stored as HTML as most content a user creates is static HTML, so when displaying content much of the HTML is displayed verbatim (but without the HTML comments), and then there's only a little bit of progressive enhancement for dynamic content.

I think you're also conflating some terms, like 'themes' and 'blocks', these are two different things and launched years apart.

[zelphirkalt]

Not the GP, but I still remember, when I was looking for where one could set an abbreviated version of a text (I don't remember, if it was a whole post's text or some description or what.). I must have searched for 30 minutes or so, until I gave up and searched in a search engine. Imagine my disbelieve, when I saw, that they use friggin HTML comments, to indicate where to make the text cutoff. In terms of storing data cleanly in the database, this is a bad design. Also sooo unintuitive. There is a field or button for everything, but suddenly I need to put HTML comments into text. What.