The Elves have been aware that the Nylasoth seems to effect Prolixians differently perhaps. I've been drinking it for years, and I'm just fine. The Cala sees no need to forbid it in Tir'an. I think I even saw some in the swamp by the Orcs. Elves may do as they wish on their islands, they may eat it, drink it, roll-it-up-and smoke it.