Salt curiously blocks bitterness. The pinch here will cut the bitterness of the coffee and allow some of the other flavors of the coffee to shine through. It's not the first time I've seen it recommended in coffee. I've been tempted to toss a pinch in my grinder when I grind the beans.
Left tap: Myrd's IPA
Right tap: Heffeweizen
Kegged: Blimey's ESB, Apfelwein, Ed's Haus Pale Ale
Fermenting: Air, but soon to be Ode-to-Arthur and more Apfelwein.