How, ARGH AND I READ IT TOO! ARGH!

does that mean you just made tthat up bro?

Hey, I was the same when I was his age. He will likely have valuable experiences and also fuck up a bunch too. Feeling happy and supportive of him (or at least pretending to) will make you a trusted resource he can talk to when he needs to. In future decades that support will likely make your relationship closer and more meaningful. Wise counsel and advice is always indicated of course within the framework of support.

It's not about your past, it is about his present. pm me if you would like more context here - I speak from experience!

Tell him to have a great time and stay in touch with him via email/phone/letters. And hey, this might be your big chance to visit Greece if you can afford it and he can put you up.

Hmmmm, I see your concern Whelk. Greece ain't the best place for your brother to go if he wants to practice being an anarchist (well, ironically, it is, but...). Sounds like he is serious about it, too, learning the language, saving money. I bet he has friends and another loose, non-hierarchical, anti-governmental structure that is encouraging him to do this. I doubt he came up with it all on his own.
I'd be worried, too. I wouldn't want my brother (or my son for that matter, who is that age and is a complete idiot) heading off to Greece to be an anarchist. That could be some dangerous shit right there. I suppose he feels mighty invincible, and Danger is currently his middle name. Yikes, that's a bummer. See if you can't convince him that being an anarchist in Branson, MO would be a much better use of his time and considerable anarchist resources.

I can't quite say anything cause I was OTHER friends who traveled into ACTUAL WARZONES when they where teenagers (buy me a drink and I'll tell you some excellent stories that include the phrase "waylaid by bandits") and I did a vanishing-act to New York one night but I can;t wrap my head around it, really? Greece? now? what?

Just make sure he'll have the money to fly back if things go south. And keep in touch.