Two translations for лежать...
There are a few translations for not currently being accepted, that I wanted to discuss here. I've reported/commented on them a few times but I think the second one in particular may be a bit controversial, so I would like to discuss them here. The first in particular probably needs a native Russian speaker's perspective, and the second particularly needs the POV's of other English speakers (though each POV is not excluded from the other question ;-) ).
1) "Sitting." True, sometimes we say something is lying/laying ;-) on something, sometimes we just say it's on something without a verb at all...but it is VERY common to say things in English like, "My keys are sitting on the table," or "That glass is sitting right on the edge." That gets across the exact same thing лежать does, even if it is not completely literal. There are even certain cases where an English speaker might use it to refer to geographic locations. I am less likely to use it that way, but it's not wrong, and there are certain cases where I might do so. "This city is sitting on a fault line" is a prime example. I'd be willing to bet in Russian that's "лежать" again.
2) "Laying." I realize I'm about to get yelled at (laid into? ;-) ) by every prescriptivist and grammar nitpicker on Duolingo for this one, but I think it is safe to say that 99% of people who reply this way when asked to translate лежать are doing so because they fully understand what the Russian word means. Yes, the currently accepted answer of "lying" is the fully correct English answer. I am not saying "laying" is the best answer. But when you say "X is laying on Y," every English speaker knows exactly what is meant by that and only a pedant of the Sheldon Cooper variety would feign a lack of understanding. (Sorry, I had to say it...I love that show.) Also, this is not the same as asking Duo to accept something like "ain't"...the confusion is much more severe for natives in this case than in a very obvious case like "ain't."
While there is an argument for forcing everyone to use absolutely perfect schoolbook English all the time, I've also noticed that Duolingo sometimes allows more idiomatic or colloquial translations, and there is a case to be made on those grounds that accepting "laying" would reward the "player's" Russian understanding even if they are making a bit of an error in their native language. I would suggest NOT accepting that answer on the REVERSE tree (because you are testing there for English skills, not Russian, and non-natives in any language should be taught their target language to a fairly exacting standard), but be a little bit laxer about that kind of English on the Russian tree since that is not the main point of that tree and there is no ambiguity about the English speaker's understanding of the Russian they are reading.
I've seem курица crop up a lot in the course so far. And if there's a sentence in which it лежит на столе, then I don't think 'laying' should be accepted.
In other cases, I very grudgingly agree with you. I often type lazy English into Duo, knowing that it will be accepted, such as leaving out apostrophes/capital letters/punctuation/etc. for the sake of speed. But still, if people type 'laying' instead of 'lying', they really should be awarded some small dunce's cap, to be permanently displayed on their profile, in return for being marked correct. I am not being a 'grammar nitpicker', but it is a completely different word with different meanings.
I will also add: the natural English way to express such things would often just be to use the verb to be. In the Swedish course, sentences involving the verb 'ligger' (literally 'to lie') all seem to accept 'is' or 'are'--'nycklarna ligger på bordet', 'the keys are lying on the table' or just 'the keys are on the table'.
It was originally a completely different word.
In many native speaker's English, the distinction is no longer as clear as you make it out to be.
Sticking to original meanings would be silly (that means "blessed, happy, prosperous", by the way, not "foolish" - unless you have kept up with language changes in the last 450 years).
"Who" is clearly on its way out and it would be very hard indeed for "Who did you see?" to be marked as wrong nowadays. "If I was..." is also accepted on Duolingo. "Lie/lay" may be heading that way as well.
Much as I personally find this mix-up annoying as well, I don't think you can put the "lie/lay" mix-up into the same kettle as, say, "their/they're/there".
I would love to have "lay" for "lie" (continue to be) marked as wrong, but I believe that this position is less defensible or less easily/strongly justifiable than for other mistakes.
Without swaying the discussion too far, who/whom may be a good illustration of the severity and pervasiveness of the confusion involving lying/laying, for native English speakers...like I said, very much in a different category from "ain't" or "axing," both of which are mistakes that have been around for centuries but are roundly condemned as wrong even now. Neither of those are threatening to actually overturn the grammatical standard the way lying/laying is.
Similarly, I suspect I am fighting a losing battle regarding incorrect forms of "all right" and "cannot" (I actually had to report another sentence in this course for rejecting "all right" in favor of the wrong but increasingly prevalent "alright"), and the fading of the word "fewer." I also use the subjunctive in English more than a lot of people do (and not just "were," but other forms that some people probably perceive as archaic), but those forms are dying.
But personally, I would apply stricter English standards to English courses, and laxer ones to courses teaching English speakers another language. (And similarly, stricter Russian standards to a course for native Russian speakers but laxer standards for Russian when they are learning another language.)
Where I'd definitely reject it would be for a course teaching English...unfortunately there IS a double standard where if a non-native makes the same error a native does, they will be judged far more harshly. :-/ I'm not so sure rejecting it on a course teaching English speakers a different language is so necessary though, since the understanding of the target language is the objective rather than perfect English.