I used a similar approach in this post to add superscripts to some items in my combobox. But using the unicode and setting the font doesn't work.
Here is the code I used:
# Define squared units
units = ['m\u00B2', 'km\u00B2']
self.dockwidget.comboBox.clear()
self.dockwidget.comboBox.addItems(oppMap_units)
self.dockwidget.comboBox.setFont(QtGui.QFont('Verdana'))
My Qt version is 4.8.5
If you're using Python 2, you must remember to use unicode:
units = [u'm\u00B2', u'km\u00B2']
Otherwise, the strings will be decoded as ascii.