This idea is not a merely theoretical one. You can see and work on one example in its earliest phase: [SeedWiki:DistributedMathSongsWiki].
Who knows similar, possibly full-flegded examples, to learn from?
I guess you mean Wiki:InterWiki.
No, the author really means the forum (seen as community aspect), dispite the absence of a unifying engine . In the meantime we can use the available intermediary tools to compensate for the lack of a DistributedWikiEngine. An AnnotationWiki is one way to build a DistributedWikiForum. Thank you for the hint, causing me to reformulate the intro of this page -- fp