For me, a comment above the IF explains the IF statement itself. For example, if the condition being tested is particularly complex.
A comment in the block below the IF or ELSE describes what’s going once the condition has been evaluated and a choice made.
So like this:
//Is this a favoured customer and do we have a promotion?
if customer.special() and monthly.hasOffer() {
//Add discount
invoice.addDiscount();
}
else {
//Add note about favoured customer scheme
invoice.addNotes(JOIN_OUR_DISCOUNT_SCHEME);
}