Oh, obviously it’s exactly the other way,
The problem is that you currently have to search forward an arbitrary number of lines to tell whether the directive is a leaf or a container. That’s not very good for parsing; ideally you have a finite amount of lookahead (right now, parsing MD requires 1 or 2 lines of lookahead, depending on your strategy in some cases). It also means that you wont’ be able to use a bare ::: without any further arguments to just mean “div”, as that would also trigger the “I’m a container!” behavior of a preceding block directive.
It would be better if there was some way to distinguish containers from leaves in the first line, or the line after. That’s why I suggested “blank line after” to mean leaf; it seems consistent with how we handle other types of blocks, and is easy to learn. (“end of container block” would also work, obviously, for those blocks where that’s unambiguous.)
btw, I’m the OP
I know, I was using it to mean “original post”, to specifically point at the first post in the thread for clarity.