Could you provide a little more detail? I’ve recently disabled user namespacing on an app I’ve deployed because I couldn’t figure out how to create an encrypted volume from within the container [1]. I think I understand the security implications and I’m comfortable with them, but I’d be really interested to know how user namespacing has saved people from real vulnerabilities in the real world.

[1] https://unix.stackexchange.com/questions/557293/how-can-i-ma...

How do you use them? Are we talking about developer desktop PC's here? Or user namespaces as part of a containerization setup?

The main use of user namespaces seems to be running stuff that wants to be root as non-root. It would seem better to simply fix all those tools to not check if they are root, and instead just try to do the thing they were trying to do.