Federation for wikis doesn't make sense, IMO. For wikis that are intended to serve as authoritative resources, you actually want to require editors to be local accounts because if they're remote, you can never end trolling / vandalism edits. Also, local accounts give more accountability for editorial control since, among other things, editing locally means editing the toolset (eg.: parser modifications, buttons, smileys, custom emojis, whatever) of the local instance.