Incidentally, is this for a particular application? Off the top of my
head, I can't think of anything that would use an untrusted config file.
An example would be sharing snippets of your emacs initialization file with
other people -- you see a lot of these floating around on the web, and some of
them are hundreds, or even thousands, of lines of Lisp code. It's not just
an issue of trust, it's also an issue of verifiability and reliability. For
instance, I don't want to make a change to my own sendmail config file that
would, without my intending it, cause sendmail to go into an infinite loop
under certain obscure conditions. I think your Quake example is also very
apropos.