Any margin account that includes KRY would be affected by the drop below $2. It does not matter whether you used it on KRY or not.

I don't use margin often, but my account is a margin qualified account and my total margin credit available dropped substantially. Had I been someone who wanted to use that for other plays, I might have liquidated KRY.

You may be right, but don't think that only people who (unwisely) buy more KRY than they can afford are affected when the stoick becomes unmarginable.