I'm coming late to this discussion but the only time I've seen this done, it's been qualified. So for example, someone will post, "I posted this story in the xyz thread but I think it's applicable here as well..." Or, "I posted this in the xyz thread but wanted to start a separate discussion about this particular aspect of it so I'm starting a new thread with the same story."
I don't find either of those things bothersome. If I've already read it, no biggie. If not, sometimes it prompts me to go see what I've missed in the other thread.
After all, the whole point of this site is to inspire discussion so if a particular story is applicable in more than one thread, I don't see anything wrong with posting it a second time.