Quote - From what I understand, on-sale items will count toward $50 minimal limit but won't be discounted by coupon (so the total discount save will be less then 30% if cart has on-sale items). A pure assumption, of course, I didn't try the coupon.

I did try it, doesn't work that way.  You have to have $50 in full price items before the coupon kicks in, at least that is how it was when I tried it yesterday.