Maybe I’m still not understanding how locales/languages work in discourse, but it was my understanding that when a user selects a different locale (say: French) than the site’s default locale (say: English), this does not entail that discourse will now only speak French with that user. For example, the discobot tutorial will still be in English, right? I don’t know, but I could imagine that also things like password reset emails and sumary emails will remain in English so that basically only the web UI changes language.
If this is so as a rule of thumb, then it’s still not evident from each Text Content element whether it affects the web UI or emails or what.
Why would you want to know? Because it is one thing to customize text elements in the site’s default language (which is what you do under Admin → Customize → Text Content) and another to then translate those new texts into the various user locales. The former is a piece of cake and the latter I have not quite figured out yet and even when you know how to do it, you still need to do it.
So, long story short: I would like to avoid customizing text elements which users with a different locale will not see unless I translate them. But in order to do that, I need to understand which text elements are governed by the site locale and which listen to the user locale.