About SharePoint:FormField and custom column

Yesterday, i had to face SharePoint again.
I created a custom type note field in which i inject custom HTML code (generated by code behind):

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1 2 3 4

<elements xmlns="http://schemas.microsoft.com/sharepoint/">  <field displayname="CustomField" group="Site Columns" id="{4a21094d-7196-4d1e-a459-ea1f7d7ee28f}" name="CustomField" restrictedmode="FALSE" richtext="TRUE" richtextmode="FullHtml" type="Note">  </field> </elements>

and a custom edit form (for the related custom content type) in which i want to show this field.

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1 2	<sharepoint:formfield controlmode="Display" fieldname="CustomField" id="CustomField" runat="server"> </sharepoint:formfield>

When i run the form, i noticed the field was blank...
What i've done to solve the problem?
This was driving me mad, i solved just setting the No value to the Append Changed to Existing Text option of the custom field.

The wanted

Voilà, smooth and clean!