Leaver system

Can u make a system similar to dota2, where if someone goes AFK u can leave without any punishment? I have punishment for leaving of the game, when i left because of AFK player wich was inactive from minute 0, i left 2minutes before map ended and now thanks of your amazing leaver buster i have ban for milion maps. Another thing. I dont know if someone was thinking about that, but when is one player AFK how is possible that im loosing rating? what is my mystake, why i need to pay for AFK in my team?