I imagine many folks are aware of this outcome, but from a quick search of the archive I didnt find a discussion.
I decided to create a new user for building the lighter profile to deploy in Singapore. Not knowing beyond the surface of how user profiles operate at the Linux level, I changed my user name in my config without adding a new user, thinking that only building a system with one profile will be faster (with the servers having problems I'm having to fallback quite a bit, so every bit of time saved helps)
But when I run $guix system roll-back, the account is broken. If I set the password again as root and then try to log back in, it crashes during loggin and in returned to the login menu. If I try to login with $sudo su blake2b, I get the error: Permission denied: /home/blake2b/.bashrc. if I remove bashrc and then try to continue, the error happens again. And its the same if I reconfigure with the new user.
So it seems this is a corner case of somewhat severe non-reproducibity (you can't even access the environment). I'm guessing it has something to do with setuid, perhaps the access rights are given to a strictly different user even if the name is the same.
Is there any fix to this?