User blog comment:StarsandPeacesigns/Vocaloids are reincarnations?!/@comment-3076833-20131125194945

When it comes to headcanons like that I like to keep them for the song series.

Like in your Servant of Evil example in that universe it could be said that Rin (who'd be in modern times) was once the Daughter of Evil in a past lifetime, or a past incarnation as you said. I don't like to think however that such things would apply for anything outside that song series since all Vocaloids have at least some varying personality and/or setting so it'd be confusing to fuse them all into one.