There are some hard-coded language values in the workflow messages configuration that should be removed.
I have not been able to ascertain if they are actually used at all, or if keys for them exist.
Each case must be tested.

/modules/pages/messageViews/publish/actions/diff/errorMessage
/modules/pages/messageViews/publish/actions/diff/failureMessage

/modules/pages/messageViews/publish/actions/review/errorMessage
/modules/pages/messageViews/publish/actions/review/failureMessage
/modules/pages/messageViews/publish/actions/review/successMessage