Bug :
Abusive players are able to disrupt games by walling around other players in co-op mode. The player that is walled in is unable to play the game any further and has to quit.
The bug empowers abusive/racist players to harass others and to disrupt the play of honest players, without any apparent way to deal with the problem. This is a major problem during co-op matchmaking play.
Suggested resolution :
In Co-op matchmaking play, players should be able to construct gates in the completed walls of other players. This would prevent abusive players from being able to surround other players with walls.