If you have a coupon discount in the cart, the amount will be displayed without a leading minus sign, making it look like the amount is added rather than subtracted from the total.
Attached is a patch (for svn trunk) that creates the displayed coupon discount from the negative value. (Additionally, the invoice view prepended the string '- ', which will break if you have negative coupons, like an extra donation you can make to a charity by giving a particular coupon code. So the patch changed this to displaying the negative amount.)
The only thing I don't like about my patch is the explicit "-" prepended to the coupon description. It might not be strictly necessary, but IMO it looks better to have "String trio (-20%)" rather than "String trio (20%)", since the latter might not indicate it's a discount and not an additional fee.
Cheers,
Reinhold
[attachment cleanup by admin]
Thanks Reinhold for your help.
I didn't use the file completely, but i did take bits of it and it solved the problem for me.
Cheers