The 3rd stage of the annual John Van Caneghem Tournament (2007).

Wow... I didn't even know that was possible.

Another example to support my point. Due to a lack of knowledge, a player could sell artifacts not only from their hero but also directly from their backpack, and by chance, they could even profit from the artifacts sold from their backpack. In essence, they could unintentionally exploit a prohibited bug because they were completely unaware of it. On the other hand, how would they prove it, and who could even prove that they didn't know? So, let's clearly state it in the rules to avoid any ambiguity. And if someone gets caught, they won't have anything to argue with.