Why am I getting reported?

At the end of a game I played recently, someone on the enemy team said "enjoy the report mf" and when I asked what he was reporting me for he said "you know what you did." I only brought this to the forums because it has happened multiple times and I'm wondering if anyone knows what it's all about. The people are always on the enemy team and they never tell me why they reported me. I know it's not for toxicity because they are always on the other team and I have all chat turned off. I'm generally pretty nice in chat anyways. If anybody says anything negative I generally just mute them and keep playing. There's a link to the match history page of the most recent game it happened in.