I think the fluent warnings for missing strings, etc, are produced here: https://searchfox.org/mozilla-central/rev/3aaca0a12a2d1463da54933bdbdae2f06fead06f/intl/l10n/Localization.h#54-69 Firefox has these enabled on nightly and debug builds, but we only get them in tor browser on debug builds. I've found the warnings useful in the past, so I would like to have them enabled on ~~alpha,~~ nightly and dev builds. Especially when we migrate to fluent in #40924