Externalization (i18n) documentation should say that whole shouldn't be split into several externalized words/group of words
In our codebase, we have sentences that are split because they include dynamic parts. For instance https://gitlab.com/gitlab-org/gitlab-ce/blob/62a600457a2192ff7487677c62eb61ba329cf2fb/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_merge_when_pipeline_succeeds.vue#L87-89.
{{ s__("mrWidget|Set by") }}
<mr-widget-author :author="mr.setToMWPSBy" />
{{ s__("mrWidget|to be merged automatically when the pipeline succeeds") }}
The problem is that sentences are not constructed in the same way in every language. For instance in French, this sentence could start with the author name, but with the words split as seen above, it's impossible to do that.
We should never split sentences and use interpolation instead (as documented in https://docs.gitlab.com/ee/development/i18n/externalization.html#interpolation).