Rosemary Penwarden said her letter telling oil executives a petroleum conference was off was satirical protest but was found guilty of forgery offences
I reads as if it was targeted and a genuine intent to confuse and be disruptive, even with the odd text at the end, but I agree it seems really minor. Especially as there don't appear to have been significant consequences as soon as organisers realised he letter was out there and issued a correction.
It's interesting the Police even considered this enough in the public interest to be investigating 7 months later, and then to prosecute at all, which makes me wonder if there's more to this. Theoretically a judge could still choose to discharge her without conviction.