Off topic from this specific incident, please address the following hypothetical future bug abuse (questionable?)
Person A uses thing he discovered to kill person B, gets reported by person B. Following investigation explains he was under the impression that it was just an unintended mechanic, and due to its inherent undocumented nature, he saw fit to use it freely.
Dev investigation decides it was in fact bug abuse, or rather, that the mechanic used was indeed a bug and not simply something that could be played off as an "unintended mechanic" / "potential future mechanic".
What happens to person A's punishment, or rather, why should any bug abuser ever be punishable if they can't really know what is or is not a bug?