I was talking about modifying the default messages. In that case, the fact that pm can be translated by AI doesn’t help. Based on my interface language, the German translation from server.de.yml of the message would be sent to me. AI would detect that as German and no translation will happen.
It’s like when you customize site texts. An example is the meta branded theme where the English texts of the search banner were changed. English-speaking users are welcomed specially to the Discourse community. While users who prefer other languages are only welcomed in general. Therefore, it seems necessary to tell them that they should search first. The fact that you only point this out to foreign-language users creates an impression that may not be intended.
Customizing text (including templates for messages) means either a lot of work to edit all translations and somehow monitor when languages are added, or deciding you don’t care that you exclude certain users from your improvements. And I think most admins miss this and therefore unintentionally do the latter. You even show some hints for hosted customers on your hosted forums only for those who use their forum in English. So I guess it’s not fair to blame admins for missing this