The debug USE flag is useless (pun intended!). xfce4-weather-plugin has a runtime debug mode which can be enabled by setting an environment variable before starting the panel. The debug USE flag doesn't have any effect and should be removed.
It looks okay to me, it's using xfce4-dev-tools and as documented in `man xfconf.eclass` you can switch --enable-debug=minimum to --enable-debug=yes by setting the USE flag and by also setting XFCONF_FULL_DEBUG=1 it turns into --enable-debug=full Both =yes and =full triggers various precompiler flags like -DXFCE_DEPRECATED and -Werror So any xfce related ebuild that supports the yes/no/minimum/full should use $(xfconf_use_debug) and have IUSE="debug" accordingly