I've tk'd several times. Always an accident except for a few blue asshats that I saw tk on purpose. I don't think I've ever been blue because of it. Maybe they assume it's an accident if you hit an enemy just before or after.
I always apologize and have never been harassed for it.
Had a good one the other day that I went back and watched the replay to see exactly what happened. I was in my Pershing and a Type59 and I were running around ganging up on bigger tanks that were alone and taking them out. We were on out third I think, he got to it first and was next to it taking a beating. One of us had tracked the heavy so he wasn't going anywhere. I rolled up on the other side and took a shot at his engine. It went right over his ass end and killed my partner...oops. The bad guy killed me with 1 more shot and drove away. There we sat. Dead. About 20m away from one another. With our guns pointing at each other. It looked like we killed each other in a dual. We both thought it was funny.