Open the scoreboard with tab. Use the Up and Down arrow keys you'll notice that X player will get highlighted. (This has several features depending on the key)
When you have X person highlighted press the delete key (Not backspace) Its hard to notice but a censored symbol will pop over that guys picture. Sometimes its UNDEr the picture though an you may only see part of the circle.
So if you press it once chances are that its muted but you may not notice because the images are messed up right now.
Playing SSF4:AE + SFxT Please say WHY you added me if you do add me or I will ignore you. PSN: Stryker105