There have been several discussions on this topic over the years and Wikidot has steadfastly rejected implementing WYSIWYG in any form. Here's just a few that I found after a quick search:
http://feedback.wikidot.com/wish:5
http://feedback.wikidot.com/wish:374
http://community.wikidot.com/wishlist:1
http://community.wikidot.com/forum/t-581/

There was some optimism based on comments from Michal in late 2006/early 2007, but it never got rolling.

Slightly off topic but I have many users in just this situation.What I do is to create a site that is made up completely of dataforms - they see no wikidot syntax at all. You design how each category will look, with headers, bold text, image positioning etc, they just have to fill in the forms. I think it works very well and makes Wikidot a very good (actually a better) alternative to Wordpress.

A few other things to consider here:

1. Saying that the current editor is not WYSIWYG is misleading, because the wiki syntax does accurately represent "what you get" (far better than many other editors, as rurwin does not match any existing user name points out, especially where lists are concerned). Not only is Wikidot's syntax is among the most readable code I've ever seen, but the Preview function works really well for most use-cases — especially for users who aren't comfortable editing the wiki syntax, and just want to see their text and pictures as they'll appear. I've already clicked Preview three times to check my syntax in this post. It's easy, once it's pointed out.
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2. There's an issue of literacy at stake here: people spend so much time on the web at this point that it's really a shame if we don't understand basic principles like opening and closing markup. I use wikidot for my writing classes, and while it does take some students a few days to get used to it, that's generally all it takes — and afterward, they're in a better position to move on to more complex web editing, reading html source code, wikimedia syntax, etc. Editing Wikidot code directly is a gateway drug to higher web literacy.
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3. There's a wealth of good documentation put out by the Wikidot community. As easy as I believe it is to work in Wikidot syntax, I recognize that I'm already attuned to a lot of things, including basics like noticing the Edit, History, and Source buttons on the toolbar. So a default feature of all my sites is a section in nav:left for instructions on how to use the wiki, and where to find more information. For people who prefer visuals to text (and isn't that what we're talking about, in the desire for WYSIWYG?), I recommend the video tutorials available at [http://www.wikidot.com/doc:video].

Sorry to swarm you with responses, Peter! I think I may have had too much coffee this afternoon, and it's making me verbose.

Saying that "people ought to be able to use the syntax" is a bit like a writer saying "my documentation is clear — you should have understood." It may be true, but it's irrelevant. The issue is that I want to get people who do not care about wikidot and actively do not want to learn its perfectly simple syntax to enter new information that they have that I don't.

When I evaluated wikis, the lack of a GUI editor was the biggest downcheck that wikidot got.