What is the reason behind this? Does giving Kunkka a Quelling Blade makes the game unbalanced?
Also, does this same rule carry-over in Dota2?
In Warcraft 3 DotA, Kunkka can't equip it. There is a bug with his splash, bonus damage from Quelling Blade damages opponent heroes as well.
Yes, he can equip it in Dota 2, where the bug is fixed.