This has changed from version 1.10, where a plain dependency on boost was defined.
yes, it requires boost[nls].
In that case I cannot agree with your resolution.
Either the dependency on boost[nls] is wrong, or wesnoth[-nls] makes no sense.
Hence, the bug is still valid, IMHO.
[ebuild R ] dev-libs/boost-1.56.0-r1:0/1.56.0 USE="nls* threads -context -debug -doc -icu -mpi -python -static-libs -tools" ABI_X86="(64) -32 (-x32)" PYTHON_TARGETS="python2_7 python3_3 -python3_4" 0 KiB
[ebuild U ] games-strategy/wesnoth-1.12 [1.10.7] USE="dbus -dedicated -doc -fribidi% -nls -server" 376,396 KiB
nls controls the install of the language files. To build it still needs boost[nls].
I understand that and I can certainly follow your position as wesnoth package maintainer. src/gettext_boost.cpp unconditionally includes boost/locale.hpp. This dependency is also documented in the INSTALL file.
Still it is awkward from my perspective. From a high level view, this is basically the interaction with Gentoo:
User: Please install wesnoth without nls.
Gentoo: Ack, will do. You still need to enable nls for a dependent package.
I have nls globally disabled, hence, this requirement feels plain wrong to me.
I filed a bug report at upstream. I propose to keep this bug open as long as it is open there.
*** Bug 544552 has been marked as a duplicate of this bug. ***