I just tried an emerge --depclean --pretend world and I had these stats:

Packages installed: 711
Packages in world: 108
Packages in system: 59
Unique package names: 576
Required packages: 590
Number to remove: 133

Alot of these packages are things like lynx, gentoo-bashcomp etc. Things
I want to keep.

What is the best way to mask out these packages so a --depclean won't
remove them? Ultimately I would love to have it so --depclean only chose
a few truely obsolete packages.