First off, this is'nt really a bug, it's more like a game weakness.
It works to do this on almost all of the boss monsters (not thoose who got self healing because they won't die)
It have'nt been fixed yet and it's still possible to use this. And the game weakness has been able to use since the lastest time they changed with the tasks and gave people another chance etc. So around a year maybe, but it's now people started to know this weakness and started to use it. If Cipsoft actually would delete someone for this, they should see this as a really serious weakness and fix it long time ago or even remove Grizzly Adam until they find away to fix it.
Sure, they can delete and ban someone, but I would be surprised.