It also works with self-built GTK+2 version:
Wow. So I was wrong with basically everything I said here. But in this case, it's fine :).
Don't know how to find the versions of Pango/Harfbuzz bundled with the official release installer.
They are listed in `ReadMe.Dependencies.Geany.txt` in the Geany installation directory: mingw-w64-i686-pango-1.43.0-3-any.pkg.tar.xz mingw-w64-i686-harfbuzz-2.6.5-1-any.pkg.tar.xz