It's a playstyle that is interesting to specific types of players which can, with proper balancing and item control, work really well. The fact that you can lose everything in minutes just makes you more careful and forces you to build smart. When your base gets destroyed you'll either just quit or start again. It's just something that's not for everyone.
And you are right, I've been searching everywhere and haven't found anything. Such a shame in my opinion, wish someone would see this and make a server like this.
Ehh... not really. I mean, in vanilla, you can be back up and running again with a half a stack of iron and some cobble. Rebuilding isn't too painful. The sum and total of your 'infrastructure' are chests and furnaces. Maybe an enchantment table and bookshelves. While the resources might be missed, they aren't unrecoverable.
In modded minecraft, however, you're looking at a very significant investment in infrastructure. Machines, refinement, storage... everything costs a lot more. Losing all that? Yea, no, that's just not something most players are interested in bothering to come back from.
It would likely have to be a custom pack, because there are several mods that come built-in with anti-griefing measures, explicitly to counter the kind of play you seek. And I have no idea how that would eventually turn out.
Most anarchy servers are mostly vanilla, maybe a few bucket/spigot plugins. I'm not aware of any with any significant amount of modding involved.
