You guys do know that choosing with who to play based on a report would mess with matchmaking right?
Players 1-10 are top 10 in matchmaking. Player 1 reports players 6-10. He has a higher probability of being matched with players 2-5 on a solo queue if they are all online. They could party, but it would affect their mmr and how the game rewards points. But in this case, they would solo queue and abuse the system.

If someone is a constant game ruiner, he deserves a punishment. Reports shouldn't be used as a "don't want to play with this guy" tool.