I emerge dwm with +savedconfig and as of yesterday, an invocation of emerge -uDN world did delete and replace my dwm config in /etc/portage/savedconfig/x11-wm
Probably because ebuild doesn't call savedconfig_pkg_postinst() from its own pkg_postinst().
Fixed in 6.1-r1. Thanks for the report! (I dropped pkg_postinst() entirely because it consists entirely of einfo messages that probably deserve a wiki page or should simply be documented in <longdescription>.)