Currently emerge --depclean --ignore-soname-deps=n will abort due to a broken soname dependency, like this example from bug 563744:
* Dependencies could not be completely resolved due to
* the following required packages not being installed:
* x86_32: libc.so.6 pulled in by:
Generally, broken soname dependencies can safely be suppressed by a REQUIRES_EXCLUDE setting in the ebuild, so they should only trigger a warning message.
There's a patch in the following branch:
I've posted it for review here:
This is in the master branch:
Released in 2.2.24.