Actually, I killed you the 2nd time. I still said you aren't allowed to do that, and apparently I was (semi) right.
I think you killed me the third time we fought using great maul but anyway, I still don't think your were right about it. When we started the duel we, in a way, both agree to use melee and great mauls. The fact I picked a great maul at the last seconds before the start of the duels isn't against the rules, since you were already using one and it is melee. You can't decide that only one side can use a particular weapon like the great maul. I also don't consider me picking a weapon from the ground in 2 of the 3 seconds of the countdown as you chasing me around.
Also, I never said that great maul was easy, like you seemed to have taken it, but that any weapon using crush-through is NOT a normal weapon thus making any duel with a weapon like that different from normal duel, no need to be so aggressive about it. Heck you even explained why in your post that a duel with it isn't normal.
I have yet to understand why not switching to a different MELEE weapon matter that much in a random, unimportant duel. I could understand if I randomly decided to switch to throwing and killed you, but I used the very same weapon as you almost at the beginning of the duel. Also if I remember correctly, you started one of the duel with a great maul, dropped it to pick a longsword when you realised I was using a sword of war and dropped it back again to pick the great maul when I picked my own great maul because I thought you were going to use the great maul again. So in a way the second duel was more a confusion than anything else.