This system doesn't work today. It is kept mostly for historical interest.
The (currently unofficial) role of User:Mediator exists on some wikipedias under various names in each language. The purpose of this account on meta is to track the way it is used, in general, and list User:Mediator/best_practices from each of the encyclopedias that have had good results with it.
At any one time, the incumbent holder of this account will be someone who can read and write fluently in at least two languages. The account will have to be handed off when there is a need to document progress in the Mediator role in a language the incumbent does not understand. For instance, it may start with a bilingual French/English user who lays out and contrasts all the ways the role has evolved on those two wikis, but then, it will be subject to a User:Mediator/handoff to someone say fluent in French and Dutch if the action heats up on say the Dutch wikipedia. Then perhaps a third person may be needed to translate back into English. Most subpages here will have to be kept in multiple languages at once. A list of User:Mediator/candidates tracks those who are active in editing them, which need not be the current holder of the account.
Related meta discussions include: