If a site with an EV cert is being spoofed using a similar-looking domain name and a DV cert, how realistically is the user going to remember that the real site is supposed to have an EV cert? (Besides just maybe remembering it for Paypal in particular.)
See also the Nordea section at https://hsivonen.fi/bank-idp/ . How is a user supposed to form a mental model about multi-server org who don't use EV consistently?
That's a legitimate concern. The bank in the link is harming itself with mixed validation and further issues with mixed content (and yes the banking industry surprisingly bad at crypto - Barclays in the UK has mixed content issues pretty frequently).
There's no simple, single answer here: you can stop validation downgrades is pinning to EV roots but browser UI is also a huge part: mobile Safari, for example, simply uses the validated legal entity as the address and keeps it on screen during the entire session (even when you scroll). Visit https://stripe.com on mobile Safari and you'll see
> _______________Stripe Inc.______________
...persistently on top of the screen throughout the entire session [1]. Other browsers don't show validated identity as effectively though.
[1] Safari should also add a country indicator to distinguish other validated legal entities called 'Stripe, Inc.' in different jurisdictions.
See also the Nordea section at https://hsivonen.fi/bank-idp/ . How is a user supposed to form a mental model about multi-server org who don't use EV consistently?