Can flavoring extracts be added to inverted sugar?
It should work, but the notion is that the flavoring should be intense so that just a little would need to be used. You don't want to substantially dilute the syrup. So a teaspoon to the two cups of water used to make the syrup would be fine. 

The other thing is that the flavoring must either be a liquid or completely dissolve in the sugar solution. What you don't want is any solid particulate matter in the cooked syrup since particles will be nucleation points upon which crystals would form. 

It is just some sugar you'd be wasting if it doesn't work. Experiment...