Current ebuilds of the mailman list server make mailman's mutable data directory the same as the install directory, i.e. /usr/local/mailman. Aside from the obvious issue of having an ebuild install _anything_ under /usr/local (bug #84708), mutable data should go under /var. The default var prefix for mailman is /var/mailman, which is appropriate. For some reason the mailman maintainer(s) changed it to /usr/local/mailman. While modern Linux installations don't generally have a problem with this, the standard FSH was set up for a reason, and it's concievable that someone might be installing mailman on a system where everything under /usr is normally set read-only between installs and updates, and under these circumstances mailman would fail. /var is generally considered the appropriate place for spools, archives and other mutable data that changes as a result of program usage.
Please, keep this in one bug... *** This bug has been marked as a duplicate of 84708 ***
Perhaps it's sufficiently related to be a duplicate, which is your call, and I would have filed it there had the summary for Bug #84708 been something more inclusive, such as "Gentoo mailman filesystem setup is totally foobar!!" ;-) Ciao
LOL... Closing, please make your point there. ;)