You can use Mediawiki syntax. It is possible that not all formatting options are supported at the moment.
You can link to internal content by using the title of a node. Use [[Node Title]] to link to the node with the corrseponding name. An alternate title can be specified like this: [[Node Title|Link title]]
External links are detected automatically. So just type http://example.com for the link. If you want a different title, use the following syntax: [http://example.com some link title].
You can use interwiki links. Type [[site:Page Title]] to link to a page on a different site. You can use the following interwiki links: