Got it. ThanksJohn,
"Harsh" means different things to different people. Flue-cured tobacco in a pipe or cigar bites the tongue because of the low pH. Harshness can be due to less than optimal harvesting time, inadequate or improper curing, inherently strong tobacco variety, odd alkaloid mixture. Heaven knows what else.
I would say that the most common "too harsh" complaint is the result of impatience: not allowing the leaf to age enough, or rest after coming out of the kiln. I would guess that commercially prepared and purchased flue-cured would narrow the possibilities down to pH and inherent strength.
Bob
John