This feature is currently disabled. See bugzilla:15622.
This is a system account. This account is used by the MediaWiki software (in a manner similar to a bot) to fix double redirects when the corresponding checkbox has been selected when moving a page. See this explanation.
Blocking this account has no effect and is thus useless. Leaving messages on this account's talkpage is useless as well, because this account is not operated by any human being. If any problems arise, please post them in the Vicipaedia:Taberna.