Some people want for the "Mute Microphone" action to mute all devices, as the "Mute playback devices" action does. See Bug 435142. Other people want for the "Mute playback devices" action to only mute the default output device rather than all of them, as the "Mute Microphone" action does. See Bug 434217. So we have two problems here: the two mute actions do different things, and there is no way to reverse the behavior of either one to satisfy the diverse use cases of our users. We should probably offer a user-facing setting to determine whether these actions mute all relevant devices, or only the default one. And then we would default to muting all devices (both input and output devices), which is probably the most common case.
I like the idea presented in bug 434217 about having 2 sets of shortcuts: one for mute all and one for mute the default device. That way we don't need a setting to have one or the other and everyone can have both. Key combination with shift is a good idea. Which one is the default (without shift) is irrelevant to me as I expect we will be able to edit these shortcuts like all the others and choose what's most comfortable for each one of us. Thank you Nate for doing an awesome job aggregating these issues.
You're welcome! Having multiple actions with different shortcuts is a thing that makes sense to me too. However since keyboard shortcuts are mostly used by experts, they are complementary to the idea presented here to choose which mute style gets activated when you trigger the default mute action, regardless of how (from the applet's context menu, from the button in the applet, from a key on your keyboard, etc)
I also like the idea of multiple shortcuts. My personal preference is that the defaults mute all input/outputs. My rationale regarding muting all microphone is that I mainly mute the microphone during online meetings so I want to be 100% sure to be muted. When I have multiple microphones (plus virtual input sources like the noise cancelling one) that can be associated to multiple applications (messed up ones like Microsoft Teams) and considering the various quirkiness of bluetooth audio devices, pipewire and so on I never trust that muting the default input is actually muting the application I am using for the meeting.