Searching for a Discount? (squarespace.com)

Probably better advice would be to just get rid of coupon code fields altogether and have special links during sales.

The fields are what trigger most people looking into that in the first place after all

Squarespace claims: "You won't find a better deal on any third-party site."

This statement is not true; the current offer code on the Back to Work podcast is for 20% off.

I've seen a superior pattern employed elsewhere: a "grab code" hyperlink on the label of the promocode's text input that brings up a modal or opens a new tab that promises a 10% (or similar) discount in return for sharing on twitter/facebook etc. It can solve two problems - people looking for promocodes can find that tab instead of websites that show your promocodes while redirecting users to your website with their referral link, AND your website will get a bit of free publicity.

I wonder if this means the end of their affiliate marketing.

Very possibly because of this: http://venturebeat.com/2013/08/12/the-big-ugly-affiliate-mar...

It doesn't look like squarespace offer an affiliate programme right now, but it seems they did and this is sensible if they'll ever want to again.