If this wasn't your 7th ban for TW/TKing I might be more lenient.
The fact that you got to -40 score means that you spent more time and energy attacking your own team than the enemy, which means you not only intentionally team wounded, but you failed to contribute to your team's effort to win. I'd call that leeching if it weren't for the fact that you actually assisted the enemy team with your actions, something more severe that just not participating.
You have to realize that while attacking your friends on the same team may be "fun" for you the game isn't about you and your friends, it's about teamwork.
I think it's reasonable to assume that the other 40+ players on your team enjoy winning more than watching their teammates pointlessly kill each other during the round. From the screenshot that Oohillac provided and the logs it's quite obvious that the round was still in full swing, remember it's never acceptable to teamkill while the round is in progress, regardless of whether the other party is your friend or not.
Having said that I'd like to remind everyone who sees this post that the manner in which you present your self and your case in your unban thread bears quite heavily on how the admin responsible reviews the ban. Being courteous and respectful with a well reasoned argument will always get you further than spastic accusations and ad hominem tactics.
In conclusion, I've decided to deny your request for an early unban. If this was one of your first or second offenses and you showed remorse I would unban you, if you hadn't managed to get -40 score, which takes dedication, I might have shortened the ban. If you think this is unjustified let me remind you that this type of behavior can result in
much more serious punishment. Learn to respect other players, everyone deserves to enjoy the game but if your version of "fun" hinders your team it is unacceptable.
