Summarizing from what I've read in this thread it seems you want to find
a way to help user find information s/he doesn't look for. 

If users aren't curious about their system they will sure have a hard
time figuring out how to fix it if needs be. PORTAGE_ELOG_* isn't really
that hard to find in the make.conf.example (even though it's new
location makes it a bit harder to find).

As others have said, there are already proper systems, documentation and
linking through other docs. Not finding this is what I'd call lazyness
or lack of google foo. Don't misunderstand me, some stuff can get ouf of
the radar of everyone, it's ok, real people are still here to point you
in the right direction.

If you find a better way to convey these information to the users, then
please surprise me. For now I think we are in a good shape.

-- 
Gilles Dartiguelongue <eva@g.o>
Gentoo