Fair enough, I can take that to some extent. Although what put this point on my radar was that I seem to recall one of the earlier questions in the lesson making an offer to select between "practise" and "practice" when constructing the sentence via touchable words (in the mobile app). So to me, that implied that the author of the lesson was aware of the two forms of spelling. So with that being so, it surprised me that when it came to a later question in the lesson, the american "practice" spelling was enforced, and that seemed a little unfair. I can't recall the specifics of my case, but I suspect the question may have been asking me to manually type in the english version of the vietnamese text, and I chose to use the british-spelling "practise" and I was marked as incorrect. If that were the case, then I wouldn't blame myself for wanting to make a note of it here. Perhaps a compromise might be to accept both spellings in this case?
Well the DL folks are really hard at work doing FAR more important things, like creating the DL bird icon which tells you, after you get slammed as "wrong" on not hearing the 'chúng' in this exercise, that you should "Keep trying! Even when you make mistakes you're still learning!!" /snark