Since this debate has been going on for a while, here I present you with a perfect example of "griefing".
IMPORTANT:
Yes you can fix that (particular example) by making npcs react hostile the third time you do it. But it is incredibly hard to "find" exploits in a game that isn't even released, so we just say that this will be in the game like this. Because there WILL be "loopholes" in the game that players will abuse to grief. Caspian & Co are no gods. They will not create a perfect simulation and human-like A.I.
The main factors, that apply here are:
-takes 0 effort (its not like you have planned a boycott over two years and if you get caught it is punishable)
-its not against any ingame or out of game rules (what? lifting your fists is now forbidden while you are close to someone? Yes you can make that law, but after a few months you will have 100 different laws all punishing something super basic, because you can use it to grief)
-the only reason to do this is to harm someone, just because you can. You aren't a rival blacksmith who tries to take him down... You are just a nobody out to do harm
CoE is no revolution of human behavior. People WILL find ways to abuse the system, without it beeing considered as "bugusing/exploiting". Lets say that you can initiate a duel with someone, just by drawing weapon/fists, which stops the crafting of someone.
Now you go to an npc, wait a bit while he is crafting a swrod, draw your fist, put them away and his progress is lost. THIS is griefing. It is allowed that you initiate a duel by drawing your weapon. It is wanted, that the progress is lost (or that you have to reheat it every time or something) when you stop it mid action. It is wanted that npcs react to threats.
Here we have a perfect exploit. Depending on how long crafting/heating takes, this can be of minor annoyance up to a total collapse of that persons buisness. And how and for what crime do you want to punish the player? He can do that all day. Its not against any known laws, its no exploit because he doesn't gain anything and and and. Its just abusing the engine to cause harm for your own fun.