Dogfooding, essentially. This guarantees that all participants eventually become broadly competent at using it.
There are newer tools to streamline common interactions, though personally I think they make the learning curve steeper in exchange for making it start off a little easier.
Plus, wiki is often an exceptionally good way to hold discussions. The fact that other contributors can, e.g. fix broken links and that freeform layout can be used... that multiple contributors can seamlessly collaborate on a single comment. It's very powerful.
Wiki for discussion also builds community and trust, because people could screw up your comments but they don't. (and if they do, it'll get fixed promptly and they'll have helpfully identified themselves as someone either totally clueless or having difficulty with self control)