On your demo and on my old version when I select an item in the editor that matches the fontname or fontsize the appropriate item in the fontname or fontsize dropdown is selected.

 

However if I follow the instructions for modifying common.config the dropdowns no longer automatically select when i select an span in the editor. The only items that work are the ones the use the value equal to an integer. If I set the value to something like 12pt or 12px it correctly puts the size in the text but does not select it in the dropdown.

 

This is a sample of the common.config: