Not me! I think that sandwich borders on sacred and I would never screw it up with horseradish. And I would never screw up horseradish by putting it on a PBJ.
When I worked in a real estate office one of my colleagues told me about a friend of his who would only order Inver House scotch and Coke. I said to him, "Why mess up a scotch?" His reply was: "Why mess up a Coke?"
To each his own.[:D]
I had dinner at the Corner Pub in Decatur, GA and saw peanut butter and jelly in the sandwich section…with horseradish optional. I can’t even imagine that – has anyone eaten that combo in anything other than a dare?