I think log_error_verbosity is a strange variable. It's useless for
expected user-facing errors but essential for unexpected errors that
indicate bugs in the code -- and you can only have it on for
everything or off for everything.
I'm finding I usually want it set to 'verbose' for anything that
PANICs or is generated by an elog() but it's just noise for anything
generated by an ereport() and is ERROR or below.
The minimum suggested change would to make it implicitly true for
PANIC and any unexpected elog()s and leave the GUC for enabling it in
the other cases.
--
greg