Don't allow customer email & order email to be different
Each WooCommerce customer with an account should be associated with only one email address - their WordPress user email address. Currently, customers can create an account with 1 email address during their first checkout, return to the site and checkout again with a 2nd email address, checkout a 3rd time with a 3rd email address, etc. It's a mess. There is no single "email address of record" for a customer.
This creates a problem when syncing to 3rd party services like ActiveCampaign or MailChimp where each contact can have only 1 email address. The address that gets synced is typically the customer email, not order email.
It would be ideal if 1 customer could have only 1 email address on file.