The default editor on new
wikia.com wikis is
WYSIWYG-only. This works
tolerably well (a bit buggy, but actively worked on).
It's not WYSIWYG only. You can switch between that and regular
wikitext whilst you're on the edit page using the "source" button, or
you can select which you want to use in your preferences. A new
version was released a couple of weeks ago, so many of the older bugs
are now resolved. There are some new ones of course, but it's
improving all the time. :)
Angela