Well, for one, their chat markup language (i.e. what they used for chat/instruction tuning). But they closed the source on that last year, so we don't know what it looks like anymore. I doubt it changed much though. Also, when you work with their models a lot for e.g. document processing, you'll find that markdown tends to work better in the context than, say, html. I've heard similar observations from people at other companies.