Honestly, I think he should just get the fine and maybe some community service. It’s not like he did some terrible evil thing, he simply caused a tiny amount of damage to huge ancient structure.
Why should he lose 5 years of his life over something simple like this? Just give him a big fine that makes him regret it, and he won’t do it again.
I said it’s relatively easy. Having both trust and anonymity online is significantly harder than in real life.
However, it is easier to pick one of those and have it online then in person. In real life, total anonymity is really hard. But online you can just use tor or something.