Fix for bug 534730 (https://github.com/gentoo/kde/commit/e29932cfdb9956cc6329643ec08be5a1c05d581f) is overly strict because it e.g. prevents kde-plasma/kdecoration from being coinstallable with kde-l10n:4. Here's a list of files from kdecoration; as you can see, there's absolutely no reason for it to conflict with kde-l10n. svist ~ # qlist kdecoration /usr/share/doc/kdecoration-5.2.1/README.md.bz2 /usr/include/KDecoration2/kdecoration2/private/decorationsettingsprivate.h /usr/include/KDecoration2/kdecoration2/private/decorationbridge.h /usr/include/KDecoration2/kdecoration2/private/decoratedclientprivate.h /usr/include/KDecoration2/kdecoration2/private/kdecoration2_private_export.h /usr/include/KDecoration2/kdecoration2/decorationdefines.h /usr/include/KDecoration2/kdecoration2/decorationshadow.h /usr/include/KDecoration2/kdecoration2/decorationsettings.h /usr/include/KDecoration2/kdecoration2/decorationbuttongroup.h /usr/include/KDecoration2/kdecoration2/decorationbutton.h /usr/include/KDecoration2/kdecoration2/decoration.h /usr/include/KDecoration2/kdecoration2/decoratedclient.h /usr/include/KDecoration2/kdecoration2/kdecoration2_export.h /usr/include/KDecoration2/KDecoration2/Private/DecorationSettingsPrivate /usr/include/KDecoration2/KDecoration2/Private/DecorationBridge /usr/include/KDecoration2/KDecoration2/Private/DecoratedClientPrivate /usr/include/KDecoration2/KDecoration2/DecorationShadow /usr/include/KDecoration2/KDecoration2/DecorationSettings /usr/include/KDecoration2/KDecoration2/DecorationButtonGroup /usr/include/KDecoration2/KDecoration2/DecorationButton /usr/include/KDecoration2/KDecoration2/Decoration /usr/include/KDecoration2/KDecoration2/DecoratedClient /usr/include/KF5/kdecoration2_version.h /usr/lib64/libkdecorations2private.so.5.2.1 /usr/lib64/libkdecorations2.so.5.2.1 /usr/lib64/cmake/KDecoration2/KDecoration2Targets-gentoo.cmake /usr/lib64/cmake/KDecoration2/KDecoration2Targets.cmake /usr/lib64/cmake/KDecoration2/KDecoration2ConfigVersion.cmake /usr/lib64/cmake/KDecoration2/KDecoration2Config.cmake /usr/lib64/libkdecorations2.so.5 /usr/lib64/libkdecorations2.so /usr/lib64/libkdecorations2private.so.5 /usr/lib64/libkdecorations2private.so
It blocks only the use flag.