The preview displays a bit different than the final tutorial. (for example, there's no page jump in the preview, whereas the final tutorial might be broke into different pages.
Also the formating code to use is based on couple of * and ** (*bold* and **italic** or the other way around, I can't remember exactly).
Also I noticed about the broken images it is when you have a lengthy tutorial with a lot of links.
To be sure, just publish and check the display of the final tutorial.
It's a bit tedious, but consider it is still a work in progess as most of the website.