Since the previous bugs I was thinking would address this issue were closed (T35677#382858 and T44186#474966) I'm opening one specifically about the request to allow interface language section by unregistered users (fix T5665) via UniversalLanguageSelector.
On our biggest multilingual wikis, Commons and Wikidata, the (monolingual) cache gets bypassed by using a gadget which makes everyone use the `uselang` URL parameter. Hence, as discussed in T114662, there are no significant performance problems with making the cache more permissive.
Using Commons' AnonymousI18N.js globally is not feasible until we can have central gadgets to deploy it ({T31272}).
Such a feature would help e.g. on this discussion [[https://pt.wikipedia.org/wiki/Wikip%C3%A9dia:Esplanada/propostas/Uso_do_portugu%C3%AAs_de_Portugal,_pt-PT_%284mar2012%29|w:pt:Wikipédia:Esplanada/propostas/Uso do português de Portugal, pt-PT (4mar2012)]]
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**See Also**:
{T44186}
{T3135}