Hi,

The basic question is: is host networking in rootless Podman any less 
secure than just running the same services uncontainerized, directly on 
the host OS, as a non-root user? Even if we exposed a rootless 
containerized service port directly to the outside world without reverse
 proxying, I don't see how this would be any riskier with host 
networking than it would be with bare metal. If the risk profile is the 
same or very nearly the same as that, I consider that sufficient.

It is not less secure than running directly on the host, generally if a option says it is insecure it refers to the ability to potentially escape the container sandbox.
If the container was started as rootless user the application is still limited to the users permissions. As mentioned in your linked blog post the biggest risk is access
to abstract sockets but that totally depends on what you have running on your system.

-- 
Paul Holzinger
Software Engineer
Red Hat
pholzing@redhat.com

Red Hat GmbH, Registered seat: Werner-von-Siemens-Ring 12, D-85630 Grasbrunn, Germany
Commercial register: Amtsgericht München/Munich, HRB 153243,
Managing Directors: Ryan Barnhart, Charles Cachera, Michael O'Neill, Amy Ross