What

The Person Merge block has a problem that is laid out in this warning in the Person & Family Field Guide:

Why

The problem with this is that any non-Admin user/role you want to enable to do person merging must have view rights to every person attribute in the system, otherwise data loss can occur during the merge. This effectively means that out of the box, only a Rock Admin can safely merge people... but even if you're willing to go through hundreds of person attributes by-hand (adding a new role to each and every one) Rock routinely adds new attributes to support new features and you'd have to remember to identify such attributes after every Rock update and add the role to those, too, or risk losing those attributes during a merge. You'd also have to remember to add the role to any new attributes you add to the system.

How

That just seems like an impossible task to maintain with any sort of accuracy. Instead, we would like to see the Person Merge block itself updated to have "superuser" powers of its own. If someone has edit rights to this block (allowing them to merge), the block itself should have admin-like rights to ensure that any and all attributes can be seen by the person-doing-the-merge and thus no special roles need to be added to every attribute.