There is nothing in the CLI that would allow you to inspect the content of a message. Remember, a message is basically just an array of bytes. It could be any kind of data - text, binary, etc. The CLI has no way to knowing how to display the data.
Thanks! I'll try to see if JBoss ON allows doing it.
Jon wont do it either, it doesnt really make sense for a management API to consumer a full message and its content, if you want to do that then just use a queue browser.