Nethaera posted a FAQ regarding the recently introduced voice chat features on the PTRs. In it she addresses one of the bigger concerns about the feature, namely the ability to moderate or disable it:

Q: How can I deal with someone who's being disruptive in voice chat?
A: While voice chat is not moderated by our in-game support team, we've provided tools to enable players to appropriately block or otherwise avoid voice chat from unwanted sources. At any time, you can right-click a player's name and select the Mute option to avoid receiving voice chat from that player. If you right-click a player's name and select the Ignore option, you will not receive voice chat or text chat from that player. To avoid having uninvited players join your private chat channel, you can set a password for the channel. We also recommend viewing the updated Parental Controls page in account management, which now includes the ability to block or alter the use of voice chat on an account. For more information on how to use the voice chat features and controls, please visit our online voice chat manual. (Parental Controls Page and Voice Chat Manual should be available soon.)

Additionally, it seems that voice masking, while not currently available, is being considered. Many players seemed concerned that revealing their actual identity in the game could alter their experience due to common misconceptions about age or gender. Voice masking, or altering the actual sound of a users voice on the fly, would provide concerned players with the ability to use the tool without harassment.