/etc/limits says this at the top: # /etc/limits contains user resource limits. # See limits(5). man 5 limits returns no manual entries, and the ebuild doesn't have a doc flag.
no real information here like `emerge info` ... my guess is you have USE=pam shadow-4.0.14-r1 provides limits(5) when USE=-pam as pam-login should be providing it ... but since newer versions of shadow have integrated pam-login back in, this isnt an issue anymore
*** Bug 147181 has been marked as a duplicate of this bug. ***