Maybe they have some purpose, but it isn't immediately obvious. I tried Tree & List mode, they're never populated.

![image](https://user-images.githubusercontent.com/13134193/33488849-04a2c8a6-d6ed-11e7-85c3-5c05f1ec5346.png)

* Bitcoin-Qt 0.15.1 for Ubuntu 16.04 x64 (from http://ppa.launchpad.net/bitcoin/bitcoin/ubuntu xenial/main amd64)

Note: I just noticed I'm *not* seeing this on Ubuntu 17.10 x64 with 0.15.1 downloaded from bitcoincore.org. 

![image](https://user-images.githubusercontent.com/13134193/33491553-9584dc62-d6f5-11e7-9ba7-e074e0e36151.png)


if (model->wallet().isLockedCoin(output))
            {
                coinControl()->UnSelect(output); 
                itemOutput->setDisabled(true);
                itemOutput->setIcon(COLUMN_CHECKBOX, platformStyle->SingleColorIcon(":/icons/lock_closed"));
            }
            
            if (coinControl()->IsSelected(output))
                itemOutput->setCheckState(COLUMN_CHECKBOX, Qt::Checked);
        }
        
        if (treeMode)
        {
            itemWalletAddress->setText(COLUMN_CHECKBOX, "(" + QString::number(nChildren) + ")");
            itemWalletAddress->setText(COLUMN_AMOUNT, BitcoinUnits::format(nDisplayUnit, nSum));
            itemWalletAddress->setData(COLUMN_AMOUNT, Qt::UserRole, QVariant((qlonglong)nSum));
        }
    }
    
    if (treeMode)
    {
        for (int i = 0; i < ui->treeWidget->topLevelItemCount(); i++)
            if (ui->treeWidget->topLevelItem(i)->checkState(COLUMN_CHECKBOX) == Qt::PartiallyChecked)
                ui->treeWidget->topLevelItem(i)->setExpanded(true);
    }
    
    sortView(sortColumn, sortOrder);
    ui->treeWidget->setEnabled(true);
}