I know this isn't the place to request unbans, but it also says that you can if it was under extraneous circumstances. I think this falls under that description.
The ban happened at 4:30pm GMT after I had been playing on a near-empty server for around 4 hours with a few of my friends. I was the only sapper on our team and in this particular game there were only about 10 people on the server. I built defences around the flag before running to the front lines where I found my friend Darth_Dimbelby who I was talking to on Discord at the time. With a mischievous smile on my face I stood in front of his cannon as he took aim at the bots, both of us chuckling the whole time. This was my first time doing something unhelpful to the team in 4 hours, or ever on this server. He fired the shot, and before my character has fully stood up again I was permanently banned from my favourite server.
Now, re-reading the rules, I was in violation of rule 11 - No arty griefing! Faliure to abide by this rule is likely to result in a temporary or permanent ban depending on the severity of the offences!
I would say that my actions are paramount to a temporary ban, which I would have laughed off and learned my lesson about your no-tolerance policy (which, having dealt with trolls myself, I completely agree with). But a permanent ban based on one incident after I had been helping the team for several hours leading up to it? I don't think this is entirely fair.