See, every day is a school day!

Just had a quick look at the code, and it never deletes the coupon, it will only ever disable them. I'm not sure if this has anything to do with the redeemed coupons and running reports. For example, it may be that if you actually delete the coupons, they then don't appear within a sales report.

You might want to test this on a demo site, and then delete out a coupon directly from the database, and see if this has any negative effects.

Absolute