Having seen the screenshot and reading the silly replies I am inclined to believe that this was an intentional teamkill.
I find it hard to grasp that someone can't notice that they've teamkilled someone, particularly having just reported the player they've splattered into the ground. There are just far too many "coincidences" in this to make it accidental.
Also, I am still a sceptic of the "banner bug" as I have, after over two years of playing, never had an incident of it, I've had no one I trust confirm or deny it. You'd notice that you've teamkilled particularly given the fact that you were aware enough to know that the victim apparently made a shout about a ban,
without naming you, and you appear to understand that it was for you (Misread). At that point, if it really was an accident, the sensible thing would have been to apologise and say that it won't happen again. Most people are understanding enough, and if you did that and told us here, checking the logs would show that, which would be enough to clear you as innocent.
1 Day ban for teamkilling.
EDIT:
I'm just saying that banner bug really excists. Before I lowered my graphic settings, some textures disappeared fromtime to time, including banners. I think that has something to do with ATI's cards
Someone I trust came forward and gave his possible explanation.
Regardless, I still find it hard to believe that you didn't notice the attack, and therefore the ban stays.
EDIT2: Aljo and I have come to an understanding that I feel is reasonable to warrant his unban, given a suggestion by him;