Yeah and in the original series one person was split into two, Jeckyll and Hyde fashion (along with some unfortunate dog-like creatures). And there were other variations. The thing is, you could do it as a matter of course. It would be simpler (and less morally fraught) than destroying the original.
I am not decrying plot devices in science fiction. I love science fiction. I enjoy suspending disbelief in the service of a good story.
The point for purposes of this conversation though is that teleportation of any flavor is not a likely explanation for anything.