Duplicating an item sets the name but display name stays the same

Question

When duplicating an item in the content tree, a modal box appears to define the Name of the new item. From my experience, the text typed in this box is set as the Name of the new item.

However, I've recently saw instances identical to mine where the duplicate item had the same text as the original item in the content tree. The only difference being the text between brackets ([]) in the right panel. This is confusing to users as they are not sure which item to choose from the content tree.

The setup I am using is Sitecore 8.0 Update-5 + Launch Sitecore 8012 WebForms. This is the same setup on which I've seen the display name behavior.

What can explain this behavior of the duplicate item command?

EDIT/solution: I was confused between the Name and the Display Name at the time of asking the question. I edited the original question for clarity. It included the following sentence originally:

I've recently saw instances identical to mine where the name of the item stayed the same as the original item and the display name was set to what was entered in the dialog box.

It turns out the Name was really set to what the user entered in the dialog box. The name of the item is displayed between brackets in the right panel when selecting an item from the content tree. What was identical between the 2 items is really the Display Name, displayed in the content tree.

As you can see in the accepted answer, the reason for the different behavior is that I did not have a Display Name on the original item but the other people had one.

Answer 1

However, I've recently saw instances identical to mine where the name of the item stayed the same as the original item and the display name was set to what was entered in the dialog box. This is confusing to users as they then have 2 items with the same name.

from the above text you have mention in your question, what I understand was you are expecting Content Editor Tree should display the Name of the item. But, by default it is displaying the "Display Name" of the item if it exists.

for example, when I enter a display name to my home item, it will look like below

And when a duplicate item is created, the Name entry box value will be used as Item Name of new Item. "Display Name" of the new item will remain same.

Is that the issue you are taking about ??

Answer 2

You can check it on item:copied and fix it. You can change the checks to meet your goals.

public class ItemEventHandler
{
    protected void SetNameToDisplayName(object sender, EventArgs args)
    {
        var copiedItem = (Item)Event.ExtractParameter(args, 1);

        if (copiedItem.Database.Name != "master"
            || !copiedItem.Paths.Path.StartsWith("/sitecore/content/")
            || copiedItem.Appearance.DisplayName == copiedItem.Name)
        {
            return;
        }

        copiedItem.Editing.BeginEdit();
        try
        {
            copiedItem.Appearance.DisplayName = copiedItem.Name;
        }
        finally
        {
            copiedItem.Editing.EndEdit();
        }
    }
}

Config

  <sitecore>
    <events>
      <event name="item:copied">
        <handler type="Sitecore.Foundation.Presentation.EventHandler.ItemEventHandler, Sitecore.Foundation.Presentation" method="SetNameToDisplayName">
          <patch:insert/>
        </handler>
      </event>
    </events>
  </sitecore>