Board Thread:General Mod Discussion/@comment-31899859-20150707111921/@comment-26065062-20150720160257

Sinthoniel wrote: When Frodo came to Lothlorien, he had problems understanding the elvish (Sindarin) spoken there. That suggests in Rivendell the official language is (modern) Quenya. Yes, the High Elves probably spoke Quenya, which would explain this, and there are also more hints to this in the books.