@PeterCxy We've had this discussion on !GNUsocial too - even whether the !fediverse tag should have a Spanish equivalent or not.
Depending on how much a profile posts, there could of course be practical issues with varying languages. It's not like you start talking Japanese in a (real, physical) room full of Swedes, right? But you rather reserve that persona for another situation, where the ones who hear you are more receptable.
As long as we haven't implemented language tagging (which is simple to do, less simple to handle well in a UI fashion unless trusting crappy automagics) it might be worth considering multiple accounts for different personas. (see .@hannes2peer@quitter.se and .@oemplojerad@quitter.se for example)