there's really no reason for this to be in x11-plugins/. it has no x11 interface, and neither does bitlbee. it's a plugin, but we don't put media-libs/gst-plugins-* in x11-plugins/ because they're not *x11* plugins. a reasonable place to put it would be in net-im/ or net-libs/, under the same line of reasoning as gst-plugins-*. another place could be www-plugins/, but that would be contrary to most users' expectations that that category be web browser plugins.
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=066841e0b9acefb71485a8a51b972d0deb2a248d