Yes, it used to be so, until very recently. Either Duolingo has adopted the new spelling, or chose to keep this strictly BP. I think it's the latter. If you're interestd in EP, here' a dictionary, that even has an option of displaying the old and the new spelling: http://www.priberam.pt/DLPO/ ("Acordo ortográfico" checkbox)
Actually, now that I think of it, this is not one of those words, because the first "c" is not silent. It sounds like "sék-são", so this is strictly BP, as I thought. Luis (the bloke that devised all of this) said something about it in a discussion. They have done it differenlty with Spanish.
The dictionary will be useful. Thank you.
Do you know whether Duolingo is collecting our input to improve the site?
Is it possible to find out how many people are at level X in any given course? I'm curious.
As far as the site itself is concerned, I know they are. If you mean the language content, I think they are, but haven't seen firsthand the improvements.
I don't think you can, the closest thing you get is the "Recommended" tab in the "Follow people" menu, but I can't fathom what the criteria for that might be.