At present, Special:MergeAccount shows, when there are accounts remaining to unify, a list of linked accounts followed by a list of unlinked accounts. Entering your password into the field below will allow accounts to be merged.
However, when the form is submitted the result is the same format as before, two lists. The user needs to manually identify which, if any, of the accounts that were in the second list have moved to the first.
I suggest presenting any accounts that have been successfully linked in a separate confirmation box above the full list of linked accounts. If no change has occurred then there should also be a message to indicate this.