Is this not fixed yet? I have the same problem with 13.2

You're right. It looks like the cells from the "Superheader" field are being selected as part of the range selection. I'll submit an issue for this. In the interim you could probably handle the ExecutingCommand event and remove/unselect any cells from that field. e.g.

  void grid_ExecutingCommand(object sender, Infragistics.Windows.Controls.Events.ExecutingCommandEventArgs e)
  {
   if (e.Command == DataPresenterCommands.Cut ||
    e.Command == DataPresenterCommands.Copy ||
    e.Command == DataPresenterCommands.Paste)
   {
    FixCellSelection(sender as DataPresenterBase);
   }
  }

  private static void FixCellSelection(DataPresenterBase dp)
  {
   var selectedCells = dp.SelectedItems.Cells;
   if (selectedCells.Count == 0)
    return;
   HashSet<Field> fieldsToRemove = new HashSet<Field>();
   foreach (var field in selectedCells[0].Field.Owner.Fields)
   {
    if (field.CellContentAlignmentResolved == CellContentAlignment.LabelOnly)
     fieldsToRemove.Add(field);
   }
   for (int i = selectedCells.Count - 1; i >= 0; i--)
   {
    if (fieldsToRemove.Contains(selectedCells[i].Field))
     selectedCells[i].IsSelected = false;
   }
  }

I created the simply test solution and got the same result. Without a superheader it works fine. There are empty collapsed cells into the grid. I saw it with "Snoop". My test solution is below

<igDP:XamDataGrid x:Name="xGrid">

            <igDP:XamDataGrid.FieldLayoutSettings>

                <igDP:FieldLayoutSettings 

                    AutoGenerateFields="False"

                    AllowClipboardOperations="Copy"

                    CopyFieldLabelsToClipboard="False"

                    AutoArrangeCells="Never" />

            </igDP:XamDataGrid.FieldLayoutSettings>

        </igDP:XamDataGrid>

public MainWindow()

{

            InitializeComponent();

            DataTable table = new DataTable();

            table.Columns.Add("Column1", typeof(string));

            table.Columns.Add("Column2", typeof(string));

            table.Rows.Add(new object[] { 100, 1000 });

            table.Rows.Add(new object[] { 100, 1000 });

            FieldSettings fs = new FieldSettings() { CellClickAction = CellClickAction.SelectCell };

            FieldLayout layout = new FieldLayout();

            Field field = new Field("Column1", "Column1") { Row = 1, Column = 0, Settings = fs };

            layout.Fields.Add(field);

            field = new Field("Column2", "Column2") { Row = 1, Column = 1, Settings = fs };

            layout.Fields.Add(field);

            field = new UnboundField()

            {

                Column = 0,

                Row = 0,

                ColumnSpan = 2,

                Label = "Superheader",

                Settings = new FieldSettings() { CellContentAlignment = CellContentAlignment.LabelOnly }

            };

            layout.Fields.Add(field);

            xGrid.FieldLayouts.Add(layout);

            xGrid.DataSource = table.DefaultView;

}