Why not? Spanish and German are widely spoken; if people want to use them to communicate, then let the market decide by virtue of the number of upvotes and responses they get.
If you see my comment below in pig Latin clearly the downvotes indicate people do not like it. Despite pig Latin to English translators existing and really there is no difference then any other language I was down voted. As far as I was aware HN is an English site and we should all try and communicate in that language when possible. Websites don’t automatically translate and don’t always do a perfect job of doing it so if we came to HN and had to try decipher all the posts it would quickly become tedious.