Thanks. Maybe switching to Authorize.net would somehow enable reCaptcha on checkout. We're using another provider (Braintree).

Can you share whether you're on the Plus plan or not, and whether you use Shopify Payments for you payment processor? We're on Plus, but do not use Shopify Payments, and for whatever reason, getting reCaptcha added to Checkout doesn't seem possible. ...

Just to clarify, this is *not* available on checkout. Only on login/create account, and comment forms. Not checkout, where it's really most needed to combat credit card fraud attacks. 

Stevo, simply adding "?discount=your_discount" to the URL didn't work for me. What does work is to use the discount permalink, with a redirect. For example:https://<your shop url>/discount/<your discount code>?redirect=/products/<your product>orhttps...