The toggle mute button is actually toggling DEAFEN off/on, for all game sounds at that (not even just voice). This is counter-intuitive and probably broken? Generally toggle mute is used for people like myself who don't want to dedicate holding down a push to talk key (open-mic) but also don't want to always be broadcasting to team-chat. This applies to Discord, Overwatch, and many similar games. I'm not sure why the functionality would be completely different in Deadlock. It seems like it's either using poor wording or was coded to mute all game sounds as opposed to the player's microphone.