I suspect that people don't trust a merchant-supplied coupon.

A also suspect this is why when you Google "landsend coupons" the #1 site is a UGC coupon-sharing site and #2 is the merchant's own site. By every traditional measure, the merchant's page should outrank the coupon site.

Why would you trust a coupon sharing site more? The merchant has an incentive to only give you some token discount, whereas the "crowd" has no such incentive. So you're more likely to trust the crowd in this scenario.

I guess it depends on whether the coupon is thought of as an incentive to buy or a cheat code.

"cheat code" is a perfect way of describing it... I think that's definitely part of the ethos of couponing. It's retail hacking for many.

That's not the same as looking at having the coupon code versus not having it.

The parent wasn't claiming this; they were merely adding a single data point about a relevant topic! I for one had not thought about pre-filling the coupon code box before, and I'm glad the parent brought it to my attention.

The grandparent tested the idea, that showing a coupon which is already filled and active, will carry an illusion of a bargain and hence the customer will be more likely to convert.

"At my company we've tested having the coupon box automatically filled in vs. not automatically filled in and we found that conversions were no higher by automatically filling it in."

What are you filling it in with and what type of discount did the coupon apply to the purchase?

So are you saying that for the purposes of testing you took a loss on the sale in order to see if there was abandonment?

Some places like Newegg put the promo code on the item page itself, so it's basically like giving it to everyone who buys the item. In this case, there's no loss on the sale.

They were substantial coupons and they were available to every customer, and posted prominently on the site and even in the cart.

We did not take any losses.