6.1-RELEASE-i386 man broken?

[J]

On 2006-07-13 (Thu) 13:25:04 [+0000], David Christensen wrote:
> Matthew Seaman wrote:
> > Please read what I wrote more carefully.  To summarize: don't set
> > $MANPATH in your environment, and the man(1) command will work
> > correctly.
> 
> Now I understand:
> 
> > The environment variable MANPATH should in general not be set, as
> > that will override the effects of /etc/manpath.config.
> 

I ran into and had to solve this problem myself when first coming to
FreeBSD, recently, as my transported Linux bash configs contained
MANPATH=$MANPATH:/custom/manpath. What I never figured out was the
rationale for this. Anyone mind me asking what's wrong with MANPATH or
why manpath.config is exclusively favored? For instance, while I have a
/usr/lib/man.conf on my Linux system and can set the default manpath
there, man happily coexists with any MANPATH. How does one add a custom
manpath without root privileges? Etc. Just curious; thanks.