In other Duolingo language courses, I have used "you" as single second person and "y'all" as plural second person. This helps keep me on track, as it drills the difference between single and plural (in this case ты and вы).
It bothers me that the Russian course doesn't accept "y'all," and I hope somebody will eventually okay these translations, not just because it recognizes the existence of "y'all" for a large swath of English speakers who do distinguish between singular and plural "yous" -- but also to actually help learn Russian.
O! moderators, hear my cry!
I could get on board with that. "You guys" and "yous/youse" should also be accepted since they're both at least as widespread as "y'all". I'd also love to see "yinz" (which is sometimes pronounced more like "yuns") but that's just my personal preference.
It's a shame that English has no discrete, standardized you(pl).