In the simple short scenario, where A owns a share, lends it to B, then B sells it to C, the share in question only has one owner: C. A doesn’t have a share any

In the simple short scenario, where A owns a share, lends it to B, then B sells it to C, the share in question only has one owner: C. A doesn’t have a share any more, they have an IOU from B for one share. B doesn’t have a share either. Only C has a share. Once the IOU comes due, B will need to acquire a share from D to give back to A, at which point both A and C own a share - but D no longer does. At no point are there any magic duplicated shareholding rights.