kdesu does not depend on sys-libs/libutempter, though it links against it. Reproducible: Always Steps to Reproduce: 1. Install kdesu without libutempter installed
This is kdesu-4.0.0, BTW.
I confirm this.
With KDE-4.2.1 locally, I see kdelibs still links to libutempter, but not kdesu. I've fixed kdelibs-4.2.1-r3.