Today I had the embarrassment of someone in my group hearing me while I was talking to a friend on discord. I checked all my in game settings and the voice chat was turned off, I couldn't see any microphone on screen, and the toggle mute keybind is unbound, and the quick menu mute option is greyed out. They only didn't stop hearing me until I turned on the option, and turned it back off in the game settings.

The person that told me they heard me said it was very quiet but noticeable, and the only way I could be sure it was off was to turn on the audio chat and mute my microphone every time I get on the game.