Tolkien famously interacted with several other writers, most notably CS Lewis, as he was working on The Lord of the Rings and his other works. But did any of those writer friends really delve into the languages and history the way he did, or were they mostly interested in his actual publishable stories?
Did Tolkien have anyone, family or friends or professional colleagues, with whom he could discuss the finer points of Quenya and his other languages, maybe even with whom he could communicate using those languages? Or was the linguistic side of Middle Earth a primarily solitary effort?