Latitude is a cool fellow, and I regret starting that convo now that he and I have messaged a bit... you're right when you said it doesn't even matter. It was just curiosity on my part that got me thinking about it. Plus, it's seems that erik would prefer we don't engage in that kind of speculation, and I'm going to try and respect that (even though I just looove thinking about such things).
Oh, and the cheater_1 discussion has really moved from here and is going on in the actual vote chess game.
I suppose this thread can die. Unless I made any spelling erors in this post.
I understand both your motivations.
"apparently a significant minority of Americans knows, and observes the difference."
I doubt that sincerely. I don't think I've ever known a single American to use practise as the verb form of practice and if one did, everyone but an anglophile (in the nicest sense) would consider it, off-hand, as a mistake. It's simply not used here. I looked in Merriam-Webster and it lists practise as a variant of practice. That generally means is usable but seldom used. So, in conclusion, it seems you were right from your side and he was right from his. It's a draw by repetition.
"Can we stop talking about grammar"
no