When posting a Confluence comment 500s on Must provide id and type for Content, fix the container field. It takes an object like id plus type page plus status current, not the bare page ID. Keep type as comment and the body in storage representation as before.

Context: Stack Overflow #28740312 (accepted answer, 4 votes): the asker POSTed a comment with container set to just the page ID and got a 500 Must provide id and type for Content. The accepted answer: container must be an object with id, type set to page, and status set to current.