This is my use case as well:
* A site in Spanish, Catalan and English.
* Offering to visitors the interface in different languages through automatic browser detection and language switcher is important.
* Pages describe the project and it is good to have all of them translated.
Until here Polylang works perfectly well. But then…
* Posts can be in any of these languages, but we don’t want the separation by languages. We don’t have the capacity to translate everything. Most readers will understand these languages at some degree anyway. We want them to find all the posts regardless of their preferred language.
* Duplication of pages with the same content is problematic. We want all users (search bots etc) to hit one page instead of many with the same content. Also, each post generates a Discourse forum automatically, and we don’t want separate forum threads created for essentially the same post.
For these reasons, Polylang for pages but not for posts would be a better scenario. Polylang solves well the case of different user groups or communities speaking different languages and not having much interaction between them. However, humans also group in truly multilingual communities where different languages can be read and spoken by the same people.