That is what the M key is for. Admins ban for intentional teamkills, not bad/reckless players.
Except that overtime it becomes rather problematic. When you're getting [5/5] multiple times a day/several times a week, clearly there is something wrong here. I've experienced amatsuka pulling off some seemingly skillful things and he's been playing for well over a year now. He isn't just bad at crpg and I don't even believe he solely teamwounds out or recklessness either. He has received multiple warnings from me for intentional teamwounding in the past as well. We had problems with this from him just a short while ago.
I checked the last 15 days worth of logs and haven't seen him getting a [5/5] once and only getting [4/5] twice(including today's incident). This is a pretty major improvement from his past and really doesn't seem to be much worse than what the average player does. We'll keep an eye on the situation, but for now no action shall be taken.