"Mysterious things" can happen when you are trying out a bunch of things with a single spack installation, or using spack in a continuous integration context, and you don't occasionally purge / move your ~/.spack folder.

It may be neat if it were possible to i.e., specify an alternative location for the purpose that path serves, or perhaps even to disable leveraging ~/.spack. Not sure if either is viable--maybe I can take a look if there's support for one of those possibilities.