Have a look at the article "Mongolian script". Now do the same thing with another browser or use Chrome as your browser.
The blocks represent the Unicode characters and I do not have a Mongolian font on my system yet. What is really cool is that Chrome shows Mongolian correctly from top to bottom. So far the lack of support for top down text in browsers is what prevents us from figuring out what we need to do in MediaWiki.
It will be cool when top down scripts are supported in most modern browsers. It enables us to support the people who read the top down scripts as well and consequently it brings us closer to what we aim to achieve.