I've been dealing with this same annoying issue. I have the Razer Krakens, and thats when it started. Physically muted the mic via the headset cord.. discord still is picking up audio from PC as if the sound coming out of my headphones are going straight to mic input and to my friends on discord. I found out when i was muting myself while eating and watching youtube or still playing the game, people in the voice channels could still hear everything that was playing on my PC. They couldn't hear me, any outside sound wasn't penetrating the mic but any audio from PC was. I have to mute myself via discord to avoid this but swapping back and forth with mute is annoying that way. I've yet to find a resolution for this problem. About to get some new headphones perhaps.