> man, by the way, is an example of a non-shell program that needs a
> namespace; part of its job is to find a collection of manual pages
> relevant to my query...
It needs a namespace, but it does not need a globally shared namespace. Indeed, the man program should not have mutate access to the standard manual page space.
The fundamental objection is not to namespaces, but to global namespaces (because these are prone to misuse by well-intentioned humans) and in particular to globally shared non-constant namespaces. A namespace that is pure constant (i.e. in both names and content) is not a communication channel.
shap