When a ComboBox is disabled, if the user tries to select the value by double click, additional new line is added to the selection
In the Demos a new line is added before the value of the ComboBox. When the same Demo is opened in a Dojo, a part from the text above the ComboBox is also highlighted. (screencast)
Only the text in ComboBox should be selected even if the widget is disabled.
The element holding the down arrow icon could be hidden when the ComboBox is disabled. - Dojo