Given that CommonMark can be converted to formats other than HTML (PDF, etc), creating a syntax for <div> may be too specific. A div is a container element, so perhaps a syntax for “containers” is what is required here.
My points could be applied to containers in general (div, aside, or other); I’m essentially asking whether we need a special syntax just for containers or if existing syntax can be reused for specific use cases. We already have syntax for block quotes, code blocks, and potentially (via an extension) pre-formatted blocks - are there use cases that warrant another syntax that could not be solved by existing block syntax with classes?