To trigger the bug:
1. Create a pool at the top level (not as a "subpool") and add some questions.
2. Save the pool, returning to the main pool page. Click "Move" under the pool name.
3. Click "Pool Manager" as the destination (essentially moving the pool back to the same place that you are moving it from)
It seems like nothing happens, but if someone logs into another account and checks their site pools, they will have a duplicate of this one. If the creator deletes the original, it deletes the pool from other people's sites, including any copies that might have been made of it (this actually would be a neat feature if the destination could be targeted and the copy was left behind, i.e, move a pool to another site).