Hi! If a global user name was hidden, the hiding should just be visible to stewards on http://meta.wikimedia.org/wiki/Special:Log/globalauth . The lines could be striked out like it's done on Special:Ipblocklist when an account was blocked with the global permission "hideuser".
As you can see it's always needed to suppress user names which contain private data although they are hidden. Another possibility is to hide Special:Log/globalauth from non-stewards like it's done with Special:Log/suppress for users without the global permission "hideuser".