Are you (all) smart? Yes. We are smart.
This messed me up, lol. The question asked to translate "Are you smart? Yes. We are smart", and I wrote "blval'a'? HISlah. maval.". It may seem silly, since it's in the context, however where I'm from, we have another word for "you" (pl.) in our creole. We'd say "Wunna smart?" rather than "You smart?", and even when I'm speaking Standard English I'd tend to differentiate and say "you all", so it was a bit off-putting. "You" just doesn't sound plural (to me at least).
I would suggest making a slight change to it, adding "(all)". I wasn't sure at first if, or rather in what way to report it, since, for one it's kinda small, and it's not so much that my answer was correct, nor that the English sentence was incorrect. I selected the latter option in report, but still wrote this, perhaps to give Mods a better idea of what the issue was (I don't know if it's an issue for anyone else) because just the report would be kinda vague.
"Sentence is incorrect or has an error" reports are pretty much useless, for the reason you mention -- they're too vague and we have no idea what you might have been thinking about.
"(all)" in parentheses is not a good option -- an English speaker would not write "Are you (all) smart?" as a natural sentence.
When translating tlhIH or its verb forms into English, we usually accept all three of "you", "you all", and "you guys", but only write "you". (And Duolingo's auto-contractor seems to accept "y'all" automatically if "you all" is an option, a bit like it accepts "can't" for "cannot" etc.)
The next bit is not something I've discussed with the others, but just my personal opinion.
Which English word or phrase to use for tlhIH, ihr, vosotros, chi, ... when teaching another language is a difficult problem, because different native speakers use different forms.
Some merely have "you" (and make no consistent distinction between SoH and tlhIH, letting context take over); some have "you all" or "y'all" or "yinz" or "ye" or "youse" or "you guys" or even "all y'all". Whichever option we would pick, there would be some people who would not be well served with it.
The German course is an interesting case study: we (the volunteer contributors to the public course) use "you" for ihr there. However, as part of Duolingo's cooperation with Pearson, many sentences entered by Pearson editors and intended for their closed course entered the public course. They seem to systematically use "you all" when they expect an answer of ihr.
And the sentence discussions are full of people asking why there is no word for "all" in the German translation -- should it not be ihr alle, for example?
So I wonder whether if we used "you all" to indicate we expect a verbal prefix appropriate for tlhIH, we would have people wanting to use Hoch in the Klingon sentence.
We could put a comment in the lesson tips and notes about how our use of "you all" just indicates that we want second person plural, and the "all" is not to be translated separately, but given the reports I've seen, a frustratingly large number of learners do not read those at all. (They're not particularly well signposted ever since crowns got rolled out, which doesn't make things better in this regard.)
Long story short: the Klingon course more or less systematically uses merely "you", whether the meaning is singular or plural. A change (to anything else) would require a huge deal of effort and is not very likely to happen, and would make things better for only some people while making it worse for others; there's no optimal solution that I can see.
Ooh, it really is difficult. Hmm, I wonder if we could suggest to the devs to somehow put default/optional translation notes for single words that have multiple meanings in the other language, more apparent and less of the answer than the hover translations, sort of like hints somewhere around the word itself.
Anyway, for the tips and notes, I myself didn't know they existed until now, I always thought that light-bulb was decorative (for some reason, and how on earth is a light-bulb "Tips and Notes", you'd expect a sticky-note, or a note pad or something. I suppose it represents ideas, idk). Perhaps they should have a bit of a preview extended below the lesson dialogue box so people know. Opening it before the lesson might be annoying. Perhaps maybe attract attention to the button by adding the number of tips and notes the user has not yet read above the button like notifications. These small numbers do quite attract ones eye, so that might be best, and it doesn't affect the gui too much. It would require new variables which might be a bit of a hassle...
lol, don't shudder at "y'all". I think all languages, including their sub-languages and variations are really cool and interesting.
I live in a country where the official language is British Standard English, but as it's in the Caribbean, we have a strong presence of our own creole. Growing up in school and at home, you'd be scolded for using that creole because it isn't "proper English", and we tend to see it as broken, and a sign of being uneducated. It wasn't until last year, I began Communication Studies at school, that I found a newfound respect for the creole, gaining a better understanding of it's complex grammar and features.
That same year a woman was nearly fired after she made a funny post to social media speaking in pure creole walking out during a fire alarm. The company said the video, in which she wore company uniform, would give them a bad reputation. So you get an idea of the mentalities towards creoles and variations, but you really have to understand the history of the variations, and the different nuances within them. Not to mention that there is not really any difference between these and languages like Standard English, which itself is also a creole. Just food for thought.