If you found a way to duplicate items you'd only get banned if you spread it through the economy. If you told a GM about it and didn't do anything with it I doubt anything would happen other than losing the items. As you said, impact is an important factor.

The shaman bug is an obvious bug that did things that weren't supposed to be possible(killing allies)(and wasn't this fixed?). The only thing unintended with zolo is how well it worked. So, how fast are we allowed to level? Standard instance 1-pull aoe power leveling is ok, athene/zolo aren't. That's a pretty wide gap of uncertainty.