Effect of Sugar on Perceived Bitterness in Coffee Abstract: Food and Function

Sugar changes the chemical structure of tea and coffee

Is this effect of sugar in water on coffee solids to be trusted? I like some coffees black (pourover, drip) and some never without sugar (espresso drinks, Aeropress) and sometimes with evaporated milk or cream. I work at a coffee shop as well. Some have said that sugar counteracts bitterness in coffees (I assume due to caffeine). Does this supposed scientific backing have any credibility?
If you are asking whether the science can be trusted, I would say yes.  The effect is already well known.  You even understand it insomuch as you apparently don't drink more concentrated brews (espresso, aerpresso) without a "masking" agent. 

All this study is doing is finding a more specific reason for the already acknowledged effect.  People commonly believe that sugar or salt "masks" the bitterness from caffeine.  This study is saying that sugar or salt are not just masking the bitterness, but actually changing the chemical properties of the caffeine in solution, thus changing the flavor.