If I run the query http://en.wikipedia.org/w/api.php?action=query&meta=userinfo&uiprop=rights while logged in, several of the user rights are listed more than once, e.g. read, edit, createtalk. For sysops the duplication is much more extensive. I assume it's just concatenating the different rights for each user group. Harmless, but it would perhaps be a little tidier if it listed each user right only once.