#. Note to translators: This is the help string for "--appstyle"
#: ../Src/main.cc:188
msgid "Application style (traditional, direct, compose or fullscreen)"

You definitely want to note that those four options MUST NOT be translated or at least must be named in english, otherwise a user running a non-english system will receive an error message when entering e.g. "direkt" (translation) instead of "direct" (original) and cannot find out the correct option.

Dasher is already translated completely into a lot of languages, see http://l10n.gnome.org/module/dasher , and most translations do not list the english options anymore.
You might want to ask the translators on gnome-i18n@ in general for fixing this.