Proposal: Language Learning
Are made up languages like Klingon on-topic? What about more realistic ones like Esperanto?
Learning constructed languages (“conlangs”) should of course be on topic, unless there was a more specific site. These can be fictional and artificial auxiliary languages, e.g. Klingon and Esperanto respectively. Some of them have more speakers and learners than many natural languages, though hardly any native speakers.
Actually, I believe the proposed conlang.stackexchange.com should be more about creating and adapting such languages. Learning them should (only) be on topic at Language Learning. Specific conlang site proposals like Lojban and Esperanto can deal with both like most existing sites on natural languages do.