CS:GO, like most other e-sports, is taken very seriously by many of it's players and requires constant teamwork, co-ordination and, ideally, a way to communicate - as such, the voice chat within the game is susceptible to abuse, with many bad actors using the voice channels to cause as much disruption as possible or be downright offensive.
Valve are now putting a stop to this tough with a new system it is developing that will apparently "help cut down" on abuse more effectively. In a nutshell, it says players that receive "significantly" more abuse reports than the average will be given a warning, and if they continue, will find themselves muted by default to all other players.
Other players can choose to unmute them, but effectively, they'll be silent to the world, at least until they've redeemed themselves and earned a significant amount of XP to reverse the mute.
Valve say as the new system is report driven, it is self-governing and means that players will "establish their own standards for communication". Hopefully this doesn't mean that the system is open to abuse though, with players muting other players over a disagreement, for example.
To prevent this, the system apparently is a bit more technical than described above, using algorithms to determine what is genuine and what is not. The reports are apparently also weighted on playtime and the frequency of reports being made.