All the cases where we had people adding generalized USE="xfce" in tree have so far been invalid. This seems to be the case for imsettings as well: The ebuild depends on xfconf, but doesn't provide any --enable/--disable flag for it. Therefore I have to assume it's purely a runtime depend only. In that case, users of Xfce will have xfconf installed already, and the whole dep and USE flag is redudant. If it's an automatic depend, and if it's really linking against libxfconf-0, use something other than USE="xfce" to describe it. Perhaps USE="xfconf".
+ 31 Jan 2011; Samuli Suominen <ssuominen@gentoo.org> imsettings-1.0.0.ebuild, + metadata.xml: + Prevent automagic linking to libxfconf-0 and rename USE="xfce" to + USE="xfconf" wrt #353117. Upstream should add --enable/--disable flag for this.
