I remember in Vanilla as a mage you could make yourself completely immune to the damage that Air Elementals caused in the Blackrock Mountain area (I think? I don't remember specifics, this was a good 9 years ago or so), and so could farm highly sought after crafting mats in bulk. Nobody got banned AFAIK, blizz just quietly patched it and moved on. I agree that some of the most fun things in WoW were unintended (Twinking, exploration, GM Island etc), it's a shame they're so much more against it these days.