I have seen people put salt in their coffee before, and at first believed it was by mistake. Later I learned it was a method of reducing bitterness. That is right, if you encounter an overly bitter coffee, before tossing it out you might give a try at a little pinch of salt to save the day. Salt as a flavor enhancer will bring out the taste in that badly brewed coffee.
Just remember good coffee needs nothing at all added to it. No salt, no sugar, no alcohol…nothing at all.
And by the way, why don’t you take a look at the post Beyond Cream and Sugar: Coffee With Cheese, Eggs and Reindeer Bones in the Food&Think blog of the Smithsonian from a couple of years ago.