Sustainable Web Development with Ruby on Rails: sustainable i18n?

Thank you for an insightful, detailed book!

There was a brief mention of internationalization (i18n) in End-to-End Example (Chapter 17). But besides a link to the Rails guides on the topic, there was no elaboration on i18n.

Given handy gems like i18n-tasks and the relatively large impact of i18n on views and tests, I think sustainable i18n could have some guidance, details, or examples.

Does Dave @davetron5000 or anyone else have ideas?