If you install dev-util/subversion with the emacs USE-flag it installs the file vc-svn.el. That's ok for emacs 21, but newer emacsen include a more enhanced and current vc-svn.el and the subversion support is broken with the older file shadowing the newer one. So subversion should not install that file if emacs 22 or 23 is installed. It also installs another emacs plugin called psvn.el. That works with all versions of emacs and can be installed unconditionally when USE=emacs is set. Reproducible: Always
*sigh* We had fixed this before, see bug #158891. *** This bug has been marked as a duplicate of bug 158891 ***