When Fluent formats translations, it returns simple strings (in the sense of primitive computer types). They can include markup which is parsed by a higher-level abstraction responsible for actually showing the translations somewhere in the UI. Take a look at https://github.com/projectfluent/fluent.js/wiki/DOM-Overlays in the experimental fluent-dom package, and their React equivalent, https://github.com/projectfluent/fluent.js/wiki/React-Overla....