The version of the Bootstrap CSS library we are using does not support RTL, so we are using a third-party library which adds RTL support to Bootstrap. Later versions of Bootstrap apparently do support RTL, but I don't know if it is worth updating.
This change is now on production.
This change is now on production, and the RTL pages are properly displaying text in an RTL manner, as expected. If & when we decide to upgrade to a newer version of Bootstrap, we can look into RTL support changes (if any) at that time. I'm marking this as Done.