The document it's happening on is a work document and I'm not at liberty to share it, also, it doesn't always happen..only when I'm not looking.
The thing is...if this is a bug, I can truly see how it could be useful, but only if the user can have input...for example, if she/he holds a modifier key while duplicating an objects, then all of the styles in that object would be duplicated as well; else, styles are not duplicated.