I am very confused why Duolingo is spending time on fictional languages from books and not working on other languages that are spoken by real people. Why is duolingo offering fictional languages?
If I recall, Klingon entered the incubator on Duolingo about the same time as Esperanto from English. I remember some mention in the press about it at the time.
One reason Klingon was added may be because of the publicity generated. That said, Klingon is also one of the most popular and developed conlangs out there, despite its being notoriously difficult.
they must have seen a strong enough case for adding klingon instead of something else. it is not terribly far-fetched to picture new people coming here just because of klingon or hv. also might be easier to get press coverage for that than most real-people languages.
at any rate, at what point would it be an acceptable idea to add a "fictional" language--when no natural language remains?
They are working on other languages spoken by real people. The addition of Klingon doesn't do any harm to the site or prevent the addition of other languages. The number of natural languages still far outnumbers the fictional ones and always will. So apart from people thinking it isn't cool, why should Klingon be a problem?
The number of natural languages still far outnumbers the fictional ones and always will.
Natural language courses for English-speakers outnumber fictional language courses on Duolingo 13:1 (I'm considering Esperanto an honorary natural language for these purposes, as it is not 'fictional' as such). Fluent speakers of these natural languages outnumber fluent speakers of the fictional languages by something more of the order of 3,000,000,000:20. Even if it turns out I am underestimating the number of fluent Klingon and HV speakers by several orders of magnitude, DL is clearly giving these languages a prominence exponentially exceeding their actual use.
Imagine that Wikipedia had only fourteen articles (let us suppose that WP articles took as long to write as DL courses), and one of them were devoted to expounding the theories of David Icke: would you consider that he would be being given undue prominence by this arrangement, or would the fact that this article would be 'far outnumbered' by (thirteen) more sensible and factual ones make it an entirely reasonable use of resources for a website that, like Duolingo, primarily exists to educate and inform people?