I don't want to just disable the key binding to invoke the HUD, I want to remove the HUD.
I notice in System Monitor that something called hud-service is taking up 65 megabytes. Besides that, I'm always invoking the HUD by accident merely by going back a page in a web browser. So I'd like to just completely uninstall anything pertaining to the HUD.
Is this possible?
I don't think is possible, since the HUD is part of Unity itself, you can check:
There they show you how to disable it
It is possible. Check this post which seems like a duplicate How can I disable hud-service?