personally, i don’t think the effect of the locale and preferred_place_id parameters should be “sticky” across pages. the fact that the website already defaults to the user’s account settings, or to the web browser’s default language, seems sufficient, and the parameters should override only on the specific pages to which they are applied.
just for reference, this is another thread by the same original poster which probably should be merged with this one: https://forum.inaturalist.org/t/inaturalist-french-version-feature-request-language-specification-in-the-url/32770.