Still trying to reproduce this, but serious enough to post this right now.

1. On one of our sites there is a CS with around 90 threads. Our client is subscribed to this.
2. I copied this CS, with children included, and pasted it on another page.
3. At that time our client recieved some 90 emails, one for each thread.

I'm not eactly sure what happened, but a couple of things seem to go wrong.

If a CS is copied, the subscribed users are copied from the original's subscription group to the copy's group. I think that's a bug; why should they be?

When the mail is sent to the subscription group, there is no test if what is sent is really a new thread or something that has been copy/pasted. Not sure if that's even possible, though.