baselayout is using GID=97 for the "input" group and dovecot is using the same GID for the "dovecot" group. And dovecot was using this GID before the "input" group was added to the baselayout: https://gitweb.gentoo.org/proj/baselayout.git/commit/share.Linux/group?id=f25b3dbc3c55e4f24d8c58ccc3278a8f6eb0def8 https://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/net-mail/dovecot/dovecot-0.99.11.ebuild?hideattic=0&revision=1.1&view=markup
Closing as acct-group/dovecot switched to GID=76