I know this is old, but there's another important reason for having Preview functionality - you need to always test every link you create. Currently, you can create links, but cannot test them, until after you save.
Having worked on Wikis for quite awhile, I have 2 rules for editing - always preview and proofread before saving, and always test every new link before saving. It certainly doesn't guarantee perfect work, but it does limit the repair work, and confusion for others because of broken URL's and typos and missed words that change the meaning.
But I suspect that Preview capability may not be available with the underlying software.