Is it ok that a user who happens to know ten different languages, posts the same content ten times?
Yes it is. Doing a translation of a text is a serious job (not considering a Googletrans a real translation) that deserves reward. Users are not obliged to vote for every version. It is expected that those who know a single language would upvote only that text, so no need to decline payout.
RE: [EN] Posting (or double-posting) in multiple languages? Read this!/[ES] ¿Publicar (o publicar doble) en varios idiomas? ¡Lee esto!