The advent of wikipedia has meant that recent aspirants to the wiki way have a sense that a wiki is a reference, an information resource, which has evolved out of the concerted effort of many editors.
That’s a great thing, but it’s not a wiki.
A wiki is a synthesis engine. A tool in a community. It allows an individual or group (usually smallish) to discover the gaps and connections in their understandings and then through exploration of the network and comparison of the nodes, fill in meaning. This means that the most important features in a wiki, for learning, are: LinkAsYouThink, BackLinks, RecentChanges, and whatever you want to call what TiddlyWiki reifies as “Missing”.