bug#53739: 28.0.91; "C-x d" fails when "emacs -Q" starts on NetBSD with plan9/bin on head of PATH

[Eli Zaretskii]

> Date: Fri, 4 Feb 2022 09:26:28 +0000 (UTC)
> From: Van Ly <van.ly@sdf.org>
> cc: Po Lu <luangruo@yahoo.com>, 53739@debbugs.gnu.org
> 
> On Fri, 4 Feb 2022, Van Ly wrote:
> 
> > On Fri, 4 Feb 2022, Eli Zaretskii wrote:
> >
> >> 
> >> So: what does "ls -l" return as exit status when using the plan9
> >> variant of 'ls'?
> >> 
> >
> 
> This also reproduces the problem.

I don't see what it reproduces, and more importantly, don't see how
this is relevant.  Please step through the code of insert-directory
and describe here what you see there when it reports the error.
Everything else is just noise, as far as investigation of this problem
is concerned.