From the Season 19 notes:
Season 19 is the Season of Eternal Conflict and with it come an awesome array of killstreak rewards! Inspired by the war waged between the High Heavens and the Burning Hells, you‘ll earn increasingly powerful effects as you unleash destruction upon your foes. So rack up those kills and clear the battlefields in the name of Sanctuary!
All players will benefit from the Pandemonium buff during Season 19. For each stack of this buff, you’ll receive a small boost to movement speed and bonus damage, ultimately capping out at 50% movement speed and 100% damage at 1000 stacks. In addition, reaching certain killstreak goals will trigger a special effect and cause even more mayhem on the battlefield:
pandemonium [ pan-duh-moh-nee-uhm ]
wild uproar or unrestrained disorder; tumult or chaos.
a place or scene of riotous uproar or utter chaos.
(often initial capital letter) the abode of all the demons.
So from the description of the seasonal buff and the definition of pandemonium itself what exactly did he do wrong here? As I see it, he and his team went to a realm of ‘udder’ chaos to ‘rack up those kills and clear the battlefields in the name of Sanctuary!’ He then took that buff to a different battlefield to cause mayhem. This guy should be rewarded for playing the seasonal theme to the absolute max, not punished. He’s brought pandemonium in-game and to the forum game at the same time.