I think we need to clear things up a little here. My understanding is that if
allow user locale is enabled, all text that is sent/displayed to the user either from the server or the client is going to be in the locale that the user has selected. Maybe @zogstrip can confirm because I don’t think it is a bug that text generated on the server is using the user’s selected locale.
Also this isn’t specific to just the bot, you can customize an email template and you’ll be faced with the same problem. What I think the right fix here is that if you customize a translation of the default site locale, all the other locales should treat its corresponding translation text as missing so that it fallbacks and uses the customized text of the default locale.