Ok. I think i forced a rollback on the server. When i restarted the server i had forgotten to add in llama craft to prevent lava spreading. The lava fire and lava spread was so cataclysmic that i had to force crash the server to save a large portion of our creations. I apologize on my own behalf for any lost progress. On the other hand, everything is working great!
So let's clear things out:
I've been building my house and my mine in the past week, on a relatively remote location, not bugging anyone for that. It was meant to be a public mine, it took me a reasonable time to build it and get the tools and blocks I left freely available to any user in the chests.
Yesterday Jkiller2911, which I had never seen on the server, went inside my house, told me "Hey I'm building my castle very near to this, please don't grief it." I said "Don't worry I'm not a griefer". I went outside and saw the initial structure of his castle. After finishing off some repairs on the mine, I left the server.
Today when I joined I found my wooden hut with some blocks randomly removed, and there was a hole on the wall, leading to a pathway. On the end of that pathway there was an empty cubic space, owned by Jkiller2911 and goettl1122, as said on a Sign Post near the entrance. I realized one of them had broke into my house and built the pathway, so I asked Jkiller2911 what the **** had happened.
He said goettl1122 was responsible for the griefing, and told him to run, whatever that means. I tried to maintain the funny situation and ran after him. First he used to try to stop me, and then he stacked obsidian in front of my house. One thing is putting insta-break dirt blocks, another one is putting 15-seconds-each-block-Obsidian right in front of my house. I said to him there would be payback. I harvested one block out of my entrance, duped it to get ~15 stacks of Obsidian and, since his castle was protected, build a gigantic wall of Obsidian to block the surroundings. While I was doing this he ran into my mine again and finished the griefing, destroying most of it and leaving lava inside my mine shaft. goettl1122 left the server soon after that, but Jkiller2911 continued his job griefing the mine. He said "Hey, how do you feel about this? I'll just ask an admin and he will delete your blocks, but your house is gone for ever, there's no way to restore it.", in a failed attempt to make me sad about it.
After that I spawned 999 TNT blocks and filled my entire mine with it. After having some fun crashing Jkiller2911's client (dude, your computer sucks), I left some TNT blocks inside his cubic square, just to render it useless.
Overall, it was fun. By banning me and protecting his contraptions, you are only making their jobs easier.